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Sample records for reversed halo sign

  1. Reversed Halo Sign: Presents in Different Pulmonary Diseases

    PubMed Central

    Zhan, Xi; Zhang, Lei; Wang, Zheng; Jin, Mulan; Liu, Min; Tong, Zhaohui

    2015-01-01

    Objective To observe the incidence of reversed halo sign in different pulmonary diseases and the pathological correspondence of reversed halo sign. Methods Retrospectively studied the high resolution computer tomography scans of all the patients who were admitted in our department with abnormal pulmonary imaging, from 1st of January 2011 to 31st of December 2013, and all the cases with reversed halo sign on the high resolution computer tomography were collected. Clinical data such as pathological findings and confirmed diagnosis of the patients with reversed halo sign on the high resolution computer tomography scan were collected and summarized. Results Of 1546 abnormal High resolution computer tomography scans 108 had a reverse halo sign present, including 108 cases were observed with reversed halo sign in the high resolution computer tomography, including 40 cases of pulmonary tuberculosis, 43 cases of cryptogenic organizing pneumonia, 16 cases of lung cancer, 7 cases of sarcoidosis, and 1 case of pulmonary cryptococcosis, 1 case of granulomatosis with polyangiitis. Reversed halo sign had a higher incidence in granulomatous diseases (16.28%) compared with non-granulomatous diseases (9.97%). Conclusions Reversed halo sign is relatively non specific; it can be observed in different lung diseases, and different phases of diseases; reversed halo sign is more commonly found in granulomatous diseases compared with non-granulomatous diseases, and is most commonly observed in pulmonary tuberculosis among the granulomatous diseases, and in cryptogenic organizing pneumonia among the non-granulomatous diseases. PMID:26083865

  2. Reversed Halo Sign: Presents in Different Pulmonary Diseases.

    PubMed

    Zhan, Xi; Zhang, Lei; Wang, Zheng; Jin, Mulan; Liu, Min; Tong, Zhaohui

    2015-01-01

    To observe the incidence of reversed halo sign in different pulmonary diseases and the pathological correspondence of reversed halo sign. Retrospectively studied the high resolution computer tomography scans of all the patients who were admitted in our department with abnormal pulmonary imaging, from 1st of January 2011 to 31st of December 2013, and all the cases with reversed halo sign on the high resolution computer tomography were collected. Clinical data such as pathological findings and confirmed diagnosis of the patients with reversed halo sign on the high resolution computer tomography scan were collected and summarized. Of 1546 abnormal High resolution computer tomography scans 108 had a reverse halo sign present, including 108 cases were observed with reversed halo sign in the high resolution computer tomography, including 40 cases of pulmonary tuberculosis, 43 cases of cryptogenic organizing pneumonia, 16 cases of lung cancer, 7 cases of sarcoidosis, and 1 case of pulmonary cryptococcosis, 1 case of granulomatosis with polyangiitis. Reversed halo sign had a higher incidence in granulomatous diseases (16.28%) compared with non-granulomatous diseases (9.97%). Reversed halo sign is relatively non specific; it can be observed in different lung diseases, and different phases of diseases; reversed halo sign is more commonly found in granulomatous diseases compared with non-granulomatous diseases, and is most commonly observed in pulmonary tuberculosis among the granulomatous diseases, and in cryptogenic organizing pneumonia among the non-granulomatous diseases.

  3. Halo and reverse halo signs in canine pulmonary computed tomography.

    PubMed

    Secrest, Scott; Sakamoto, Kaori

    2014-01-01

    The halo sign (HS) and reverse halo sign (RHS) are radiologic signs identified on pulmonary computed tomography (CT) in people. The HS is described as a circular area of ground-glass attenuation surrounding a pulmonary nodule or mass. The RHS is defined as a focal, rounded area of ground-glass attenuation surrounded by a more or less complete ring of consolidation. These signs have been identified in a variety of diseases in people. The purpose of this retrospective study was to determine if the HS and RHS occur in dogs with pulmonary disease and to determine if they are associated with a particular disease process. In addition, the appearance of the HS and RHS was correlated with the histopathologic changes. Our results indicate that the HS and RHS are not common signs identified in dogs with pulmonary disease with an HS noted in five cases and an RHS in 4 of the 33 dogs that met the inclusion criteria. An association between the HS (P-value 0.8163) or RHS (P-value 0.5988) and neoplasia, infectious/inflammatory, and other disease processes was not identified using a Fisher's exact test. The HS was identified in neoplastic, infectious, and inflammatory conditions, with the RHS identified in neoplastic and infectious diseases and a lung lobe torsion. Histologically, the HS and RHS were caused by tumor extension, necrosis, and/or hemorrhage of the pulmonary parenchyma. © 2014 American College of Veterinary Radiology.

  4. The diagnostic value of halo and reversed halo signs for invasive mold infections in compromised hosts.

    PubMed

    Georgiadou, Sarah P; Sipsas, Nikolaos V; Marom, Edith M; Kontoyiannis, Dimitrios P

    2011-05-01

    The halo sign is a CT finding of ground-glass opacity surrounding a pulmonary nodule or mass. The reversed halo sign is a focal rounded area of ground-glass opacity surrounded by a crescent or complete ring of consolidation. In severely immunocompromised patients, these signs are highly suggestive of early infection by an angioinvasive fungus. The halo sign and reversed halo sign are most commonly associated with invasive pulmonary aspergillosis and pulmonary mucormycosis, respectively. Many other infections and noninfectious conditions, such as neoplastic and inflammatory processes, may also manifest with pulmonary nodules associated with either sign. Although nonspecific, both signs can be useful for preemptive initiation of antifungal therapy in the appropriate clinical setting. This review aims to evaluate the diagnostic value of the halo sign and reversed halo sign in immunocompromised hosts and describes the wide spectrum of diseases associated with them.

  5. The Diagnostic Value of Halo and Reversed Halo Signs for Invasive Mold Infections in Compromised Hosts

    PubMed Central

    Georgiadou, Sarah P.; Sipsas, Nikolaos V.; Marom, Edith M.

    2011-01-01

    The halo sign is a CT finding of ground-glass opacity surrounding a pulmonary nodule or mass. The reversed halo sign is a focal rounded area of ground-glass opacity surrounded by a crescent or complete ring of consolidation. In severely immunocompromised patients, these signs are highly suggestive of early infection by an angioinvasive fungus. The halo sign and reversed halo sign are most commonly associated with invasive pulmonary aspergillosis and pulmonary mucormycosis, respectively. Many other infections and noninfectious conditions, such as neoplastic and inflammatory processes, may also manifest with pulmonary nodules associated with either sign. Although nonspecific, both signs can be useful for preemptive initiation of antifungal therapy in the appropriate clinical setting. This review aims to evaluate the diagnostic value of the halo sign and reversed halo sign in immunocompromised hosts and describes the wide spectrum of diseases associated with them. PMID:21467021

  6. The reversed halo sign: update and differential diagnosis

    PubMed Central

    Godoy, M C B; Viswanathan, C; Marchiori, E; Truong, M T; Benveniste, M F; Rossi, S; Marom, E M

    2012-01-01

    The reversed halo sign is characterised by a central ground-glass opacity surrounded by denser air–space consolidation in the shape of a crescent or a ring. It was first described on high-resolution CT as being specific for cryptogenic organising pneumonia. Since then, the reversed halo sign has been reported in association with a wide range of pulmonary diseases, including invasive pulmonary fungal infections, paracoccidioidomycosis, pneumocystis pneumonia, tuberculosis, community-acquired pneumonia, lymphomatoid granulomatosis, Wegener granulomatosis, lipoid pneumonia and sarcoidosis. It is also seen in pulmonary neoplasms and infarction, and following radiation therapy and radiofrequency ablation of pulmonary malignancies. In this article, we present the spectrum of neoplastic and non-neoplastic diseases that may show the reversed halo sign and offer helpful clues for assisting in the differential diagnosis. By integrating the patient's clinical history with the presence of the reversed halo sign and other accompanying radiological findings, the radiologist should be able to narrow the differential diagnosis substantially, and may be able to provide a presumptive final diagnosis, which may obviate the need for biopsy in selected cases, especially in the immunosuppressed population. PMID:22553298

  7. Reversed halo sign in acute pulmonary embolism and infarction.

    PubMed

    Casullo, Joseph; Semionov, Alexandre

    2013-06-01

    The reversed halo sign, originally described in cryptogenic organizing pneumonia, has been observed in a variety of pulmonary diseases, including pulmonary embolism (PE). To describe the computed tomographic (CT) findings in patients with the reversed halo sign and acute PE at initial presentation and in subsequent scans. Contrast-enhanced CT examinations of 12 patients with the reversed halo sign and acute PE were analyzed retrospectively. The diagnosis of pulmonary embolism was made by CT angiography in 11 cases and by a routine contrast-enhanced scan of the chest in the other case. Follow-up scans of seven patients and follow-up radiographs of two patients were also examined retrospectively. The average age of the patients was 49 years (range, 21-80 years). Seven (58%) patients were women. Six patients had no significant medical history, and six patients had deep venous thrombosis initially. The reversed halo sign was observed as a single lesion in 10 patients; in two patients, two lesions were found. The lesions, all pleural-based, occurred more frequently in the lower lobes and were associated with acute thromboemboli in segmental and subsegmental pulmonary arteries of the corresponding segment. Ten (10/14, 71%) lesions displayed an ellipsoid configuration, two (2/14, 14%) had a pyramidal shape, and two involved an almost entire pulmonary segment. The average largest dimension was 3.9 cm (range, 2.1-6.7 cm). All lesions subtended one or more bronchovascular bundles; three (3/14, 21%) showed air-bronchograms, and a thromboembolus was identified in the subtended arteries in nine (9/14, 64%) lesions. In succeeding CT scans (eight lesions) and follow-up radiographs (three lesions), the lesions became smaller, and the majority evolved into pleural-based linear scars by 7 months. The reversed halo sign very likely corresponds to pulmonary infarction in patients with acute PE. Its recognition may have important clinical implications. © 2013 The Foundation Acta

  8. Reversed halo sign in active pulmonary tuberculosis: criteria for differentiation from cryptogenic organizing pneumonia.

    PubMed

    Marchiori, Edson; Zanetti, Gláucia; Irion, Klaus Loureiro; Nobre, Luiz Felipe; Hochhegger, Bruno; Mançano, Alexandre Dias; Escuissato, Dante Luiz

    2011-12-01

    The purpose of this study was to compare the morphologic characteristics of the "reversed halo" sign caused by tuberculosis with those caused by cryptogenic organizing pneumonia (COP) and to determine whether high-resolution CT (HRCT) can differentiate between these two conditions. We retrospectively reviewed the HRCT scans of patients with the reversed halo sign caused by active tuberculosis and HRCT scans of patients with the reversed halo sign caused by COP. The study included 12 patients with active pulmonary tuberculosis (10 women and two men) and 10 patients with biopsy-proven COP (five women and five men). Tuberculosis was diagnosed by culture of sputum, bronchoalveolar lavage, or biopsy specimen. All patients underwent HRCT, and the images were reviewed by two chest radiologists who reached decisions by consensus. HRCT scans of all patients with active tuberculosis showed reversed halos with nodular walls; in most cases (10/12), we also observed nodules inside the halos. None of the HRCT scans of the COP cases reviewed had halos with nodular walls or nodules inside them. We also observed parenchymal abnormalities, such as consolidation, ground-glass, and linear opacities, associated with the reversed halo sign. Neither the number of reversed halo sign lesions nor the associated parenchymal lesions discriminated between tuberculosis and COP. Nevertheless, the association of the reversed halo sign with nodular walls or nodules inside the halo was seen only in tuberculosis patients. Although COP is considered the most frequent cause of the reversed halo sign, the presence of nodular walls or nodules inside the reversed halo strongly favors a diagnosis of active pulmonary tuberculosis rather than COP.

  9. [Clinical features of reversed halo sign in cryptogenic organizing pneumonia].

    PubMed

    Inoue, Yukihisa; Yoshimura, Nobuyuki; Shimada, Hiroyuki; Saito, Hiroaki; Shimizu, Kyouko; Kurata, Kiyoko; Kobayashi, Akiko; Yamazaki, Keiichi; Jin, Yasuto; Inase, Naohiko

    2011-02-01

    Reversed halo sign (RHS) is often seen in computed tomography (CT) scans of cryptogenic organizing pneumonia (COP). To investigate its clinical features, we retrospectively reviewed 30 cases of COP in 13 men and 17 women, whose age range 28 to 73, with a mean of 58.4 years. All diagnoses were made with transbronchial lung biopsy (TBLB), but it took an average of 24.8 days from the first visit until the diagnosis of COP. RHS was seen in 7 cases (23%) and multiple RHSs were seen in 3 cases. We treated 5 cases (71%) with steroids. Their CT images showed parenchymal abnormalities which started as nodular lesions, then enlarged, and then the central lesion changed into ground-glass opacities, until finally, RHS was formed. The presence of RHS does not necessarily indicate a marked difference in the clinical course of COP. In conclusion, in the present series RHS was a phase of the clinical course of COP, and was useful to diagnose COP.

  10. Reversed halo sign on high-resolution CT of cryptogenic organizing pneumonia: diagnostic implications.

    PubMed

    Kim, Sang Jin; Lee, Kyung Soo; Ryu, Young Hoon; Yoon, Young Cheol; Choe, Kyu Ok; Kim, Tae Sung; Sung, Ki Jun

    2003-05-01

    The aim of our study was to evaluate the usefulness of the reversed halo sign on high-resolution CT in the diagnosis of cryptogenic organizing pneumonia. Between 1996 and 2001, we saw 31 patients with biopsy-proven cryptogenic organizing pneumonia. During the same period, we also saw 30 patients with non-cryptogenic organizing pneumonia diseases, from which cryptogenic organizing pneumonia should be differentiated: Wegener's granulomatosis (n = 14), diffuse bronchioloalveolar carcinoma (n = 10), chronic eosinophilic pneumonia (n = 5), and Churg-Strauss syndrome (n = 1). Two independent observers analyzed CT findings and recorded how frequently the so-called reversed halo sign (central ground-glass opacity and surrounding air-space consolidation of crescentic and ring shape) was seen on high-resolution CT. The most common patterns of parenchymal abnormalities of cryptogenic organizing pneumonia were ground-glass opacity (28/31 patients, 90%) and consolidation (27/31, 87%). The ground-glass opacity pattern showed random distribution, and the consolidation pattern showed subpleural or peribronchovascular (20/27 patients, 74%) distribution with predominance in the middle or lower lung zone. The reversed CT halo sign was seen in six (19%) of 31 patients with cryptogenic organizing pneumonia and in none of the patients with the diseases that needed to be differentiated from cryptogenic organizing pneumonia on CT. The reversed halo sign, although seen only in one fifth of patients with the disease, appears relatively specific to make a diagnosis of cryptogenic organizing pneumonia on CT.

  11. [A case of cryptogenic organizing pneumonia showing reversed halo sign on computed tomography of the chest].

    PubMed

    Arai, Toru; Inoue, Yoshikazu; Ando, Seijitsu; Inoue, Koji; Tsuyuguchi, Kazunari; Suzuki, Katsuhiro; Hayashi, Seiji; Kitaichi, Masanori; Akira, Masanori; Sakatani, Mitsunori

    2007-08-01

    A 56-year-old female non-smoker complained of general fatigue and pyrexia. Laboratory examination revealed elevation of white blood cells (WBC) 10200/microl and C-reactive protein (CRP) 13.3mg/dl. Chest radiograph showed bilateral patchy and ring-shaped consolidations in both lungs. Chest computed tomography (CT) revealed multiple round ground glass opacities fringed with consolidation, namely the "reversed halo sign". Transbronchial lung biopsy specimens showed polypoid granulation tissue in terminal air spaces, consistent with an organizing pneumonia pattern. Clinical findings suggesting collagen vascular diseases and drug induced lung diseases were not recognized, thus cryptogenic organizing pneumonia (COP) was diagnosed. High dose methylprednisolone therapy improved her condition, and the ring-shaped opacities on chest CT resolved. She relapsed twice during approximately five years after the disease onset. Chest CT at the recurrences revealed subpleural patchy consolidations without formation of the "reversed halo sign". The sign was originally supposed to be specific for cryptogenic organizing pneumonia. However, other diseases like sarcoidosis and paracoccidioidomycosis have been reported to show this sign. The meaning of the "reversed halo sign" should be examined based on the accumulation of more cases.

  12. Reversed halo sign on thin-section CT in a patient with non-specific interstitial pneumonia

    PubMed Central

    Hong, S H; Kang, E-Y; Shin, B K; Shim, J J

    2011-01-01

    We present a case of non-specific interstitial pneumonia (NSIP) with reversed halo sign on thin-section CT. A 52-year-old female presented with a cough and New York Heart Association (NYHA) class 2 dyspnoea of 4 months duration. A chest radiograph showed poorly defined, patchy ground-glass opacities in both lungs. Thin-section CT demonstrated the reversed halo sign, which is a central ground-glass opacity surrounded by crescent or ring-shaped areas of consolidation in multifocal areas. Multifocal patchy ground-glass opacity and consolidation and enlarged paratracheal, hilar and subcarinal lymph nodes were also shown. Video-assisted thoracic surgical (VATS) lung biopsy was performed, and histopathology revealed cellular NSIP. PMID:21511742

  13. The halo sign: HRCT findings in 85 patients

    PubMed Central

    Alves, Giordano Rafael Tronco; Marchiori, Edson; Irion, Klaus; Nin, Carlos Schuler; Watte, Guilherme; Pasqualotto, Alessandro Comarú; Severo, Luiz Carlos; Hochhegger, Bruno

    2016-01-01

    ABSTRACT Objective: The halo sign consists of an area of ground-glass opacity surrounding pulmonary lesions on chest CT scans. We compared immunocompetent and immunosuppressed patients in terms of halo sign features and sought to identify those of greatest diagnostic value. Methods: This was a retrospective study of CT scans performed at any of seven centers between January of 2011 and May of 2015. Patients were classified according to their immune status. Two thoracic radiologists reviewed the scans in order to determine the number of lesions, as well as their distribution, size, and contour, together with halo thickness and any other associated findings. Results: Of the 85 patients evaluated, 53 were immunocompetent and 32 were immunosuppressed. Of the 53 immunocompetent patients, 34 (64%) were diagnosed with primary neoplasm. Of the 32 immunosuppressed patients, 25 (78%) were diagnosed with aspergillosis. Multiple and randomly distributed lesions were more common in the immunosuppressed patients than in the immunocompetent patients (p < 0.001 for both). Halo thickness was found to be greater in the immunosuppressed patients (p < 0.05). Conclusions: Etiologies of the halo sign differ markedly between immunocompetent and immunosuppressed patients. Although thicker halos are more likely to occur in patients with infectious diseases, the number and distribution of lesions should also be taken into account when evaluating patients presenting with the halo sign. PMID:28117474

  14. The halo sign: HRCT findings in 85 patients.

    PubMed

    Alves, Giordano Rafael Tronco; Marchiori, Edson; Irion, Klaus; Nin, Carlos Schuler; Watte, Guilherme; Pasqualotto, Alessandro Comarú; Severo, Luiz Carlos; Hochhegger, Bruno

    2016-01-01

    The halo sign consists of an area of ground-glass opacity surrounding pulmonary lesions on chest CT scans. We compared immunocompetent and immunosuppressed patients in terms of halo sign features and sought to identify those of greatest diagnostic value. This was a retrospective study of CT scans performed at any of seven centers between January of 2011 and May of 2015. Patients were classified according to their immune status. Two thoracic radiologists reviewed the scans in order to determine the number of lesions, as well as their distribution, size, and contour, together with halo thickness and any other associated findings. Of the 85 patients evaluated, 53 were immunocompetent and 32 were immunosuppressed. Of the 53 immunocompetent patients, 34 (64%) were diagnosed with primary neoplasm. Of the 32 immunosuppressed patients, 25 (78%) were diagnosed with aspergillosis. Multiple and randomly distributed lesions were more common in the immunosuppressed patients than in the immunocompetent patients (p < 0.001 for both). Halo thickness was found to be greater in the immunosuppressed patients (p < 0.05). Etiologies of the halo sign differ markedly between immunocompetent and immunosuppressed patients. Although thicker halos are more likely to occur in patients with infectious diseases, the number and distribution of lesions should also be taken into account when evaluating patients presenting with the halo sign. O sinal do halo consiste em uma área de opacidade em vidro fosco ao redor de lesões pulmonares em imagens de TC de tórax. Pacientes imunocompetentes e imunodeprimidos foram comparados quanto a características do sinal do halo a fim de identificar as de maior valor diagnóstico. Estudo retrospectivo de tomografias realizadas em sete centros entre janeiro de 2011 e maio de 2015. Os pacientes foram classificados de acordo com seu estado imunológico. Dois radiologistas torácicos analisaram os exames a fim de determinar o número de lesões e sua distribui

  15. Velocity selective optical pumping resonance sign reversal

    NASA Astrophysics Data System (ADS)

    Krasteva, A.; Slavov, D.; Todorov, G.; Cartaleva, S.

    2013-03-01

    We report experimental and theoretical examinations of the peculiarities in Velocity Selective Optical Pumping (VSOP) resonance behavior at open and closed hyperfine transition spectra of Cs atoms (on the D2 line), confined in optical cell with thickness L = 6λ, where λ = 852 nm. For linear and circular polarizations of the irradiating light, open transitions exhibit reduced absorption (fluorescence) VSOP resonances whose contrast increases with atomic concentration and light intensity. However, in case of closed transition the situation is different, the enhanced absorption (fluorescence) VSOP resonance reverses its sign with the atomic concentration and light intensity. Theoretical analysis based on the density matrix formalism, taking into account the statistical tensors describing atomic population and longitudinal alignment, shows that the VSOP resonance sign reversal at the closed transition can be attributed to the efficiency reduction of population transfer by the spontaneous decay with atomic source temperature.

  16. The frequency and clinical significance of the halo sign in focal nodular hyperplasia of the liver.

    PubMed

    Wu, Size; Tu, Rong; Liu, Guangqing; Shi, Yusen

    2012-12-01

    The purpose of this study was to investigate the frequency of the halo sign in focal nodular hyperplasia (FNH) of the liver and its clinical significance. Archives of 19 patients (6 men, mean age 35 years +/- 11, range 22-53 years and 13 women, mean age 39 years +/- 15, range 17-66 years) diagnosed from April 2005 through March 2012 with FNH were reviewed. All images were analyzed by three readers in a panel in order to depict the characteristics of the liver lesions and established in consensus a diagnosis. The halo appearance of lesions was focused upon. The halo sign was found in 6 FNHs (31.6%, 6/19). The mean size of the FNHs was 34.2 mm +/- 7.2 (range 23-47 mm). Characteristics of FNH appear were various in gray-scale ultrasound and color Doppler flow imaging, CT and MRI, and combined use of different modalities may enable diagnosis definitely. All patients with FNH reviewed were consistent with previous diagnoses. The halo sign was found in a high number of patients in this study, which implies that the halo sign may be not rare in FNH on sonography, and absence and presence of the halo sign may not help identifying FNH.

  17. CT halo sign as an imaging marker for response to adoptive cell therapy in metastatic melanoma with pulmonary metastases.

    PubMed

    Shrot, Shai; Schachter, Jacob; Shapira-Frommer, Ronnie; Besser, Michal J; Apter, Sara

    2014-06-01

    The halo sign refers to a zone of ground-glass attenuation surrounding a pulmonary nodule. Pulmonary metastatic nodules exhibiting a halo sign are seen mainly in hypervascular tumours. We describe the appearance of a halo sign following treatment of adoptive transfer of autologous tumour-infiltrating lymphocytes (TIL) to melanoma patients with lung metastases. The study included 29 melanoma patients with pulmonary metastases who received TIL therapy. Pre- and post-treatment chest CTs were retrospectively reviewed for the presence of a halo sign and its correlation with therapeutic response. A pulmonary halo sign was not seen in any pre-treatment CT. It was observed in four of 12 patients who responded to the therapy but not in those who failed to respond. Significant differences were found between response ratio in patients in whom post-TIL halo sign appeared compared with those without the halo sign (p = 0.02). The appearance of a CT halo sign in melanoma with lung metastases following TIL therapy may indicate antitumoral effect and a good response to therapy. Our findings emphasize the importance of applying new assessment criteria for immunological anticancer therapies. Tumour-infiltrating lymphocytes (TIL) in melanoma patients is a promising novel immunotherapy. Post-therapy pulmonary halo sign appeared in one-third of TIL responders . Pulmonary halo sign may serve as an imaging marker for antitumoral activity.

  18. Perisplenic halo on /sup 99m/Tc sulfur colloid scintigraphy: a sign of mild ascites

    SciTech Connect

    Shih, W.J.; Domstad, P.A.; Deland, F.H.

    1982-04-01

    A patient with acute parenchymal liver disease whose /sup 99m/Tc sulfur colloid (SC) liver/spleen scan showed a perisplenic halo in the posterior view (supine position) proved to have mild ascites at the time of autopsy. The signs of mild and massive ascites are briefly discussed.

  19. Kidney neoplasms: renal halo sign after percutaneous radiofrequency ablation--incidence and clinical importance in 101 consecutive patients.

    PubMed

    Schirmang, Todd C; Mayo-Smith, William W; Dupuy, Damian E; Beland, Michael D; Grand, David J

    2009-10-01

    To describe the incidence and clinical importance of the renal halo sign after percutaneous radiofrequency ablation (RFA) of renal neoplasms. Institutional review board approval was obtained for this HIPAA-compliant retrospective study. The study population consisted of 101 consecutive patients with 106 solid renal neoplasms that were treated with percutaneous RFA. Postablation computed tomographic (CT) and magnetic resonance (MR) images were retrospectively reviewed by three board-certified radiologists to determine the presence of the renal halo sign. Statistical analyses were performed to determine reader agreement and assess the effect that tumor size and location, radiofrequency (RF) applicator type, RFA treatment time and success, maximum RFA treatment temperature, and number of RF applications performed had on development of the renal halo sign. The renal halo sign developed in 79 (75%) of the 106 ablated tumors. Average imaging follow-up lasted 25 months (range, 1-98 months). The renal halo sign appeared, on average, 6 months (range, 1 month to 3 years) after RFA. The renal halo sign resolved in five (6%) of 79 tumors treated. Interobserver agreement for the presence of the renal halo sign was high. Tumor size and location, RF applicator type, RFA treatment time and success, maximum RFA treatment temperature, and number of RF applications performed were not independent predictors of renal halo sign development. The renal halo sign is seen in 75% of patients after percutaneous RFA of renal neoplasms. It may decrease in size over time; however, it rarely disappears. It is important to recognize this sign, as it can be mistaken for recurrent tumor or angiomyolipoma by radiologists who are not familiar with RFA.

  20. Palm Reversal Errors in Native-Signing Children with Autism

    PubMed Central

    Shield, Aaron; Meier, Richard P.

    2012-01-01

    Children with autism spectrum disorder (ASD) who have native exposure to a sign language such as American Sign Language (ASL) have received almost no scientific attention. This paper reports the first studies on a sample of five native-signing children (four deaf children of deaf parents and one hearing child of deaf parents; ages 4;6 to 7;5) diagnosed with ASD. A domain-general deficit in the ability of children with ASD to replicate the gestures of others is hypothesized to be a source of palm orientation reversal errors in sign. In Study 1, naturalistic language samples were collected from three native-signing children with ASD and were analyzed for errors in handshape, location, movement and palm orientation. In Study 2, four native-signing children with ASD were compared to 12 typically-developing deaf children (ages 3;7 to 6;9, all born to deaf parents) on a fingerspelling task. In both studies children with ASD showed a tendency to reverse palm orientation on signs specified for inward/outward orientation. Typically-developing deaf children did not produce any such errors in palm orientation. We conclude that this kind of palm reversal has a perceptual rather than a motoric source, and is further evidence of a “self-other mapping” deficit in ASD. PMID:22981637

  1. Is It Time to Include CT “Reverse Halo Sign” and qPCR Targeting Mucorales in Serum to EORTC-MSG Criteria for the Diagnosis of Pulmonary Mucormycosis in Leukemia Patients?

    PubMed Central

    Caillot, Denis; Valot, Stéphane; Lafon, Ingrid; Basmaciyan, Louise; Chretien, Marie Lorraine; Sautour, Marc; Million, Laurence; Legouge, Caroline; Payssot, Alexandre; Dalle, Frédéric

    2016-01-01

    In 23 leukemia patients with proven (n = 17) or possible (n = 6) pulmonary mucormycosis (PM), the presence of reversed halo sign on computed tomography was strongly associated with the positivity of quantitative polymerase chain reaction assays targeting Mucorales in the serum, confirming the value of these two tools for the diagnosis of PM in this setting. PMID:28101518

  2. [A Case Strongly Suspected of Being Pulmonary Toxocariasis Showing Multiple Pulmonary Nodules with a Disappearing and Reappearing Halo Sign].

    PubMed

    Takakura, Akira; Harada, Shinya; Katono, Ken; Igawa, Satoshi; Katagiri, Masato; Yanase, Nobuo; Masuda, Noriyuki

    2015-03-01

    We report herein on a case strongly suspected of being pulmonary toxocariasis. A 22-year-old Indonesian man referred to our hospital presented with abnormal chest shadows upon medical examination. He had no symptoms. He did not have any pets nor did he eat raw beef or chicken. Hematological examination revealed eosinophilia and elevation of IgE. Chest computed tomography revealed 3 pulmonary nodules with the halo sign. We suspected a parasite infection and performed antiparasite antibody testing. Ascaris suum was slightly positive on the screening test. As specific antibody against the larval excretory-secretory products of Toxocara canis, measured at the National Institute of Infectious Diseases, was positive (level 3 up to 8). Subsequently, the abnormal chest shadows disappeared. However, two months later, 2 pulmonary nodules with the halo sign reappeared in other places. Diagnostic therapy with albendazole was performed for 8 weeks. Mild hepatic impairment emerged during therapy, but it was within the allowed range. Thereafter, the results improved for the imaging findings, eosinophilia, serum IgE level, and specific antibody. The antibody level became negative two months after the treatment had ended. We should consider toxocariasis in the differential diagnosis of migratory nodular shadows with the halo sign on chest computed tomography, and immunoserological testing is useful for the diagnosis.

  3. Reverse Conversion Schemes for Signed-Digit Number Systems: A Survey

    NASA Astrophysics Data System (ADS)

    Chakraborty, Madhu Sudan

    2016-12-01

    Although signed-digit number systems have received a considerable attention, the transformation of signed-digit numbers back into the conventional forms, known as reverse conversion, is still a performance bottleneck of signed-digit arithmetic. In this paper, a literature survey of reverse conversion schemes for signed-digit number systems is performed on the basis of the articles published from recognized platforms for the past few decades. The survey reveals some specific problems of this field, which need further investigations.

  4. Palm Reversal Errors in Native-Signing Children with Autism

    ERIC Educational Resources Information Center

    Shield, Aaron; Meier, Richard P.

    2012-01-01

    Children with autism spectrum disorder (ASD) who have native exposure to a sign language such as American Sign Language (ASL) have received almost no scientific attention. This paper reports the first studies on a sample of five native-signing children (four deaf children of deaf parents and one hearing child of deaf parents; ages 4;6 to 7;5)…

  5. Current Drive in a Ponderomotive Potential with Sign Reversal

    SciTech Connect

    N.J. Fisch; J.M. Rax; I.Y. Dodin

    2003-07-30

    Noninductive current drive can be accomplished through ponderomotive forces with high efficiency when the potential changes sign over the interaction region. The effect can practiced upon both ions and electrons. The current drive efficiencies, in principle, might be higher than those possible with conventional radio-frequency current-drive techniques, since different considerations come into play.

  6. Hall voltage sign reversal in thin superconducting films

    NASA Technical Reports Server (NTRS)

    Ferrell, Richard A.

    1992-01-01

    A novel approach to the superconducting Hall effect is developed, based on the opposing drift of the thermally excited quasi-particles. These collide quasi-elastically with the hydrodynamics superfluid velocity field circulating for outside the core of a vortex, thereby transferring momentum to the latter. The predicted Hall angle, by BCS theory, is of the order of kBTc divided by the Fermi energy, has sign opposite to that in the normal state because of the backflow, and disappears at low temperature.

  7. Transition from Sign-Reversed to Sign-Preserved Cooper-Pairing Symmetry in Sulfur-Doped Iron Selenide Superconductors.

    PubMed

    Wang, Qisi; Park, J T; Feng, Yu; Shen, Yao; Hao, Yiqing; Pan, Bingying; Lynn, J W; Ivanov, A; Chi, Songxue; Matsuda, M; Cao, Huibo; Birgeneau, R J; Efremov, D V; Zhao, Jun

    2016-05-13

    An essential step toward elucidating the mechanism of superconductivity is to determine the sign or phase of the superconducting order parameter, as it is closely related to the pairing interaction. In conventional superconductors, the electron-phonon interaction induces attraction between electrons near the Fermi energy and results in a sign-preserved s-wave pairing. For high-temperature superconductors, including cuprates and iron-based superconductors, prevalent weak coupling theories suggest that the electron pairing is mediated by spin fluctuations which lead to repulsive interactions, and therefore that a sign-reversed pairing with an s_{±} or d-wave symmetry is favored. Here, by using magnetic neutron scattering, a phase sensitive probe of the superconducting gap, we report the observation of a transition from the sign-reversed to sign-preserved Cooper-pairing symmetry with insignificant changes in T_{c} in the S-doped iron selenide superconductors K_{x}Fe_{2-y}(Se_{1-z}S_{z})_{2}. We show that a rather sharp magnetic resonant mode well below the superconducting gap (2Δ) in the undoped sample (z=0) is replaced by a broad hump structure above 2Δ under 50% S doping. These results cannot be readily explained by simple spin fluctuation-exchange pairing theories and, therefore, multiple pairing channels are required to describe superconductivity in this system. Our findings may also yield a simple explanation for the sometimes contradictory data on the sign of the superconducting order parameter in iron-based materials.

  8. Reversible change of birefringence sign by optical and thermal processes in an azobenzene polymethacrylate

    SciTech Connect

    Rodriguez, F.J.; Sanchez, C.; Villacampa, B.; Alcala, R.; Cases, R.; Millaruelo, M.; Oriol, L.

    2005-01-10

    Birefringence ({delta}n) induced in an azobenzene polymethacrylate by combination of biphotonic and thermotropic processes has subsequently been changed in sign by room temperature illumination with linearly polarized blue light. The sign of {delta}n can be reversed again, by simply heating up the film to 100 deg. C. This change of {delta}n between positive and negative values can be repeated several times. Besides, by appropriate choice of film thickness and blue light irradiation conditions the same absolute value for positive and negative {delta}n values can be obtained.

  9. Magnetoresistance manipulation and sign reversal in Mn-doped ZnO nanowires

    SciTech Connect

    Sapkota, Keshab R.; Chen, Weimin; Maloney, F. Scott; Poudyal, Uma; Wang, Wenyong

    2016-10-14

    We report magnetoresistance (MR) manipulation and sign reversal induced by carrier concentration modulation in Mn-doped ZnO nanowires. At low temperatures positive magnetoresistance was initially observed. When the carrier concentration was increased through the application of a gate voltage, the magnetoresistance also increased and reached a maximum value. However, further increasing the carrier concentration caused the MR to decrease, and eventually an MR sign reversal from positive to negative was observed. An MR change from a maximum positive value of 25% to a minimum negative value of 7% was observed at 5 K and 50 KOe. The observed MR behavior was modeled by considering combined effects of quantum correction to carrier conductivity and bound magnetic polarons. Finally, this work could provide important insights into the mechanisms that govern magnetotransport in dilute magnetic oxides, and it also demonstrated an effective approach to manipulating magnetoresistance in these materials that have important spintronic applications.

  10. Magnetoresistance manipulation and sign reversal in Mn-doped ZnO nanowires

    SciTech Connect

    Sapkota, Keshab R.; Chen, Weimin; Maloney, F. Scott; Poudyal, Uma; Wang, Wenyong

    2016-10-14

    We report magnetoresistance (MR) manipulation and sign reversal induced by carrier concentration modulation in Mn-doped ZnO nanowires. At low temperatures positive magnetoresistance was initially observed. When the carrier concentration was increased through the application of a gate voltage, the magnetoresistance also increased and reached a maximum value. However, further increasing the carrier concentration caused the MR to decrease, and eventually an MR sign reversal from positive to negative was observed. An MR change from a maximum positive value of 25% to a minimum negative value of 7% was observed at 5 K and 50 KOe. The observed MR behavior was modeled by considering combined effects of quantum correction to carrier conductivity and bound magnetic polarons. This work could provide important insights into the mechanisms that govern magnetotransport in dilute magnetic oxides, and it also demonstrated an effective approach to manipulating magnetoresistance in these materials that have important spintronic applications.

  11. Magnetoresistance manipulation and sign reversal in Mn-doped ZnO nanowires

    PubMed Central

    Sapkota, Keshab R.; Chen, Weimin; Maloney, F. Scott; Poudyal, Uma; Wang, Wenyong

    2016-01-01

    We report magnetoresistance (MR) manipulation and sign reversal induced by carrier concentration modulation in Mn-doped ZnO nanowires. At low temperatures positive magnetoresistance was initially observed. When the carrier concentration was increased through the application of a gate voltage, the magnetoresistance also increased and reached a maximum value. However, further increasing the carrier concentration caused the MR to decrease, and eventually an MR sign reversal from positive to negative was observed. An MR change from a maximum positive value of 25% to a minimum negative value of 7% was observed at 5 K and 50 KOe. The observed MR behavior was modeled by considering combined effects of quantum correction to carrier conductivity and bound magnetic polarons. This work could provide important insights into the mechanisms that govern magnetotransport in dilute magnetic oxides, and it also demonstrated an effective approach to manipulating magnetoresistance in these materials that have important spintronic applications. PMID:27739442

  12. Magnetoresistance manipulation and sign reversal in Mn-doped ZnO nanowires.

    PubMed

    Sapkota, Keshab R; Chen, Weimin; Maloney, F Scott; Poudyal, Uma; Wang, Wenyong

    2016-10-14

    We report magnetoresistance (MR) manipulation and sign reversal induced by carrier concentration modulation in Mn-doped ZnO nanowires. At low temperatures positive magnetoresistance was initially observed. When the carrier concentration was increased through the application of a gate voltage, the magnetoresistance also increased and reached a maximum value. However, further increasing the carrier concentration caused the MR to decrease, and eventually an MR sign reversal from positive to negative was observed. An MR change from a maximum positive value of 25% to a minimum negative value of 7% was observed at 5 K and 50 KOe. The observed MR behavior was modeled by considering combined effects of quantum correction to carrier conductivity and bound magnetic polarons. This work could provide important insights into the mechanisms that govern magnetotransport in dilute magnetic oxides, and it also demonstrated an effective approach to manipulating magnetoresistance in these materials that have important spintronic applications.

  13. Magnetoresistance manipulation and sign reversal in Mn-doped ZnO nanowires

    NASA Astrophysics Data System (ADS)

    Sapkota, Keshab R.; Chen, Weimin; Maloney, F. Scott; Poudyal, Uma; Wang, Wenyong

    2016-10-01

    We report magnetoresistance (MR) manipulation and sign reversal induced by carrier concentration modulation in Mn-doped ZnO nanowires. At low temperatures positive magnetoresistance was initially observed. When the carrier concentration was increased through the application of a gate voltage, the magnetoresistance also increased and reached a maximum value. However, further increasing the carrier concentration caused the MR to decrease, and eventually an MR sign reversal from positive to negative was observed. An MR change from a maximum positive value of 25% to a minimum negative value of 7% was observed at 5 K and 50 KOe. The observed MR behavior was modeled by considering combined effects of quantum correction to carrier conductivity and bound magnetic polarons. This work could provide important insights into the mechanisms that govern magnetotransport in dilute magnetic oxides, and it also demonstrated an effective approach to manipulating magnetoresistance in these materials that have important spintronic applications.

  14. Magnetoresistance manipulation and sign reversal in Mn-doped ZnO nanowires

    DOE PAGES

    Sapkota, Keshab R.; Chen, Weimin; Maloney, F. Scott; ...

    2016-10-14

    We report magnetoresistance (MR) manipulation and sign reversal induced by carrier concentration modulation in Mn-doped ZnO nanowires. At low temperatures positive magnetoresistance was initially observed. When the carrier concentration was increased through the application of a gate voltage, the magnetoresistance also increased and reached a maximum value. However, further increasing the carrier concentration caused the MR to decrease, and eventually an MR sign reversal from positive to negative was observed. An MR change from a maximum positive value of 25% to a minimum negative value of 7% was observed at 5 K and 50 KOe. The observed MR behavior wasmore » modeled by considering combined effects of quantum correction to carrier conductivity and bound magnetic polarons. Finally, this work could provide important insights into the mechanisms that govern magnetotransport in dilute magnetic oxides, and it also demonstrated an effective approach to manipulating magnetoresistance in these materials that have important spintronic applications.« less

  15. Impurity scattering rate and coherence factor in vortex core of sign-reversing s -wave superconductors

    NASA Astrophysics Data System (ADS)

    Nagai, Yuki; Kato, Yusuke

    2010-11-01

    We investigate the impurity scattering rates for quasiparticles in vortex cores of sign-reversing s -wave superconductors as a probe to detect the internal phase difference of the order parameters among different Fermi surfaces. The impurity scattering rates and coherence factors are related to quasiparticle interference effect by the scanning tunneling microscopy and spectroscopy technique. With use of the Born and Kramer-Pesch approximations for the Andreev bound states, we show that the sign-reversed forward scatterings are dominant in vortex cores. Owing to the coherence factor in vortex cores of ±s -wave superconductors, the impurity scattering rate of the Andreev bound states has a characteristic distribution on the Fermi surfaces. For comparison, the impurity scattering rates in vortex cores of s -wave and d -wave superconductors are also discussed.

  16. Sign reversals of the output autocorrelation function for the stochastic Bernoulli-Verhulst equation

    SciTech Connect

    Lumi, N. Mankin, R.

    2015-10-28

    We consider a stochastic Bernoulli-Verhulst equation as a model for population growth processes. The effect of fluctuating environment on the carrying capacity of a population is modeled as colored dichotomous noise. Relying on the composite master equation an explicit expression for the stationary autocorrelation function (ACF) of population sizes is found. On the basis of this expression a nonmonotonic decay of the ACF by increasing lag-time is shown. Moreover, in a certain regime of the noise parameters the ACF demonstrates anticorrelation as well as related sign reversals at some values of the lag-time. The conditions for the appearance of this highly unexpected effect are also discussed.

  17. Selective Surface Charge Sign Reversal on Metallic Carbon Nanotubes for Facile Ultrahigh Purity Nanotube Sorting.

    PubMed

    Wang, Jing; Nguyen, Tuan Dat; Cao, Qing; Wang, Yilei; Tan, Marcus Y C; Chan-Park, Mary B

    2016-03-22

    Semiconducting (semi-) single-walled carbon nanotubes (SWNTs) must be purified of their metallic (met-) counterparts for most applications including nanoelectronics, solar cells, chemical sensors, and artificial skins. Previous bulk sorting techniques are based on subtle contrasts between properties of different nanotube/dispersing agent complexes. We report here a method which directly exploits the nanotube band structure differences. For the heterogeneous redox reaction of SWNTs with oxygen/water couple, the aqueous pH can be tuned so that the redox kinetics is determined by the availability of nanotube electrons only at/near the Fermi level, as predicted quantitatively by the Marcus-Gerischer (MG) theory. Consequently, met-SWNTs oxidize much faster than semi-SWNTs and only met-SWNTs selectively reverse the sign of their measured surface zeta potential from negative to positive at the optimized acidic pH when suspended with nonionic surfactants. By passing the redox-reacted nanotubes through anionic hydrogel beads, we isolate semi-SWNTs to record high electrically verified purity above 99.94% ± 0.04%. This facile charge sign reversal (CSR)-based sorting technique is robust and can sort SWNTs with a broad diameter range.

  18. First Signs of Flow Reversal Within a Separated Turbulent Boundary Layer

    NASA Astrophysics Data System (ADS)

    Hammerton, Jared; Lang, Amy

    2015-11-01

    A shark's skin is covered in millions of microscopic scales that have been shown to be able to bristle in a reversing flow. The motive of this project is to further explore a potential bio-inspired passive separation control mechanism which can reduce drag. To better understand this mechanism, a more complete understanding of flow reversal within the turbulent boundary layer is required. In order to capture this phenomenon, water tunnel testing at The University of Alabama was conducted. Using a long flat plate and a rotating cylinder, a large turbulent boundary layer and adverse pressure gradient were generated. Under our testing conditions the boundary layer had a Reynolds number of 200,000 and a boundary layer height in the testing window of 5.6 cm. The adverse pressure gradient causes the viscous length scale to increase and thus increase the size of the individual components of the turbulent boundary layer. This will make the low speed streaks approximately 1 cm in width and thus large enough to measure. Results will be presented that test our hypothesis that the first signs of flow reversal will occur within the section of lowest momentum located furthest from the wall, or within the low speed streaks. This Project was funded by NSF REU Site Award 1358991.

  19. Majorana-Time-Reversal Symmetries: A Fundamental Principle for Sign-Problem-Free Quantum Monte Carlo Simulations

    NASA Astrophysics Data System (ADS)

    Li, Zi-Xiang; Jiang, Yi-Fan; Yao, Hong

    2016-12-01

    A fundamental open issue in physics is whether and how the fermion sign problem in quantum Monte Carlo (QMC) simulations can be solved generically. Here, we show that Majorana-time-reversal (MTR) symmetries can provide a unifying principle to solve the fermion sign problem in interacting fermionic models. By systematically classifying Majorana-bilinear operators according to the anticommuting MTR symmetries they respect, we rigorously prove that there are two and only two fundamental symmetry classes which are sign-problem-free and which we call the "Majorana class" and "Kramers class," respectively. Novel sign-problem-free models in the Majorana class include interacting topological superconductors and interacting models of charge-4 e superconductors. We believe that our MTR unifying principle could shed new light on sign-problem-free QMC simulation on strongly correlated systems and interacting topological matters.

  20. Optical anisotropy and sign reversal in layer-by-layer assembled films from chiral nanoparticles.

    PubMed

    Liang, Zhumei; Bernardino, Kalil; Han, Jishu; Zhou, Yunlong; Sun, Kai; de Moura, André F; Kotov, Nicholas A

    2016-10-06

    Chiral anisotropy and related optical effects at the nanoscale represent some of the most dynamic areas of nanomaterials today. Translation of optical activity of chiral semiconductor and metallic nanoparticles (NPs) into optoelectronic devices requires preparation of thin films from chiral NPs on both flat and curved surfaces. In this paper we demonstrate that chiral NP films can be made via layer-by-layer assembly (LBL) using negatively charged chiral CdS NPs, stabilized by d- and l-cysteine and positively charged polyelectrolytes, as building blocks. LBL coatings from NPs combine simplicity of preparation and strong optical activity. Circular extinction measurements using circular dichroism instruments indicate that the film possess four chiroptical bands at 280, 320, 350, and 390 nm. The latter two bands at 390 and 350 nm are associated with the band gap transitions (chiral excitons), while the former two are attributed to transitions involving surface ligands. When NPs are assembled in LBL films, the rotatory activity and the sign for circular extinction associated with the electronic transition in the inorganic core of the NPs is conserved. However, this is not true for circular extinction bands at short wavelengths: the sign of the rotatory optical activity is reversed. This effect is attributed to the change of the conformation of surface ligands in the polyelectrolyte matrix, which was confirmed both by semi-empirical and density functional (DFT) quantum mechanical calculations. Circular dichroism spectra calculated using a DFT algorithm closely match the experimental spectra of CdS NPs. These findings indicate that the spectroscopic methods sensitive to chirality of the surface ligands can be used to investigate fine structural changes in the surface layer of nanocolloids. Strong rotatory optical activity of nanostructured semiconductor films opens the possibilities for new polarization-based optical devices.

  1. Unconventional superconductivity with a sign reversal in the order parameter of LaFeAsO1-xFx.

    PubMed

    Mazin, I I; Singh, D J; Johannes, M D; Du, M H

    2008-08-01

    We argue that the newly discovered superconductivity in a nearly magnetic, Fe-based layered compound is unconventional and mediated by antiferromagnetic spin fluctuations, though different from the usual superexchange and specific to this compound. This resulting state is an example of extended s-wave pairing with a sign reversal of the order parameter between different Fermi surface sheets. The main role of doping in this scenario is to lower the density of states and suppress the pair-breaking ferromagnetic fluctuations.

  2. Anomalous electric birefringence behavior of sonicated DNA fragments as observed in reversing-pulse transients and steady-state sign reversal: a multicomponent approach.

    PubMed

    Yamaoka, Kiwamu

    2007-04-15

    Anomalous electric birefringence signals of a sonicated and column-fractionated medium-size calf thymus DNA sample (bp=570) in Na(+) solutions were measured at 7 degrees C. The reversing-pulse electric birefringence (RPEB) signal pattern was theoretically calculated in the low electric field region for two axially symmetric models coexisting in equilibrium in solution. The RPEB theory is based on the electric dipole moment due to ion-fluctuation along the longitudinal direction and the electric polarizability anisotropy (Deltaalpha'), together with various electric and optical parameters assigned to the models. An analytical method was developed for the steady-state birefringence of the two-component system in a wide range of electric fields. The NaDNA samples exhibit complex RPEB patterns mixed with negative- and positive-going profiles. An experimental RPEB signal of NaDNA at an absorbance (A(260)) of 8 was fitted to theoretical curve at weak electric fields. The anomalous RPEB signal was attributed to the component 2, which shows a dip in the buildup and another in the reverse processes with a positive sign and a larger relaxation time. For the component 1, a normal DNA profile with negative sign is associated with a narrow dip in the reverse and a faster relaxation time in the decay signal. The field-strength dependence of observed steady-state birefringence delta(infinity) could be fitted for NaDNA at A(260)=8 by the SUSID orientation function with saturated ionic and electronic moments. An apparent positive maximum and the sign reversal in delta(infinity) at weak electric fields is an interplay between the positive component 2 with positive optical factor Deltag and negative Deltaalpha' and the negative component 1 with negative Deltag and positive Deltaalpha'. Possible conformation of two DNA components involved in solution was estimated.

  3. Temperature-induced sign reversal of biaxiality observed by conoscopy in some ferroelectric Sm-C* liquid crystals

    NASA Astrophysics Data System (ADS)

    Song, Jang-Kun; Chandani, A. D. L.; Fukuda, Atsuo; Vij, J. K.; Kobayashi, Ichiro; Emelyanenko, A. V.

    2007-07-01

    We have studied various ferroelectric liquid crystals to find the average molecular direction of the shortest axis in the perfectly unwound state by using tilted conoscopic measurements. We find that there exist two types of temperature dependencies of the biaxiality. Some materials exhibit increasing biaxiality while others show decreasing biaxiality with increasing temperature. The former shows a temperature-induced sign reversal of biaxiality. Three different physical mechanisms are identified as responsible for the emergence of biaxiality: (i) anisotropic fluctuations of the long molecular axis, (ii) a biased rotation around the long axis, and (iii) the local field effect. By means of a simple theoretical investigation, we conclude that these two types of trends are due mainly to the opposite signs of the biaxial order parameter C , which represents the second mechanism: the biased rotation around the long axis. This means that the central phenyl planes of molecules belonging to materials having biaxiality that increases with temperature are oriented on the average parallel to the tilt plane (the shortest index of refraction axis normal to the tilt plane), and, on the contrary, in those of the others molecules are oriented perpendicular to the tilt plane (the shortest index of refraction axis lying in the tilt plane). Thus, the direction of the phenyl ring plane of the liquid crystal molecules determines the different temperature dependencies of the biaxiality. It is also shown that the phenomenon of sign reversal of the biaxiality is due to the competitive contributions of the first and second physical mechanisms.

  4. Experimental Evidence for Sign Reversal of the Hall Coefficient in Three-Dimensional Metamaterials.

    PubMed

    Kern, Christian; Kadic, Muamer; Wegener, Martin

    2017-01-06

    Effectively inverting the sign of material parameters is a striking possibility arising from the concept of metamaterials. Here, we show that the electrical properties of a p-type semiconductor can be mimicked by a metamaterial solely made of an n-type semiconductor. By fabricating and characterizing three-dimensional simple-cubic microlattices composed of interlocked hollow semiconducting tori, we demonstrate that sign and magnitude of the effective metamaterial Hall coefficient can be adjusted via a tori separation parameter-in agreement with previous theoretical and numerical predictions.

  5. Experimental Evidence for Sign Reversal of the Hall Coefficient in Three-Dimensional Metamaterials

    NASA Astrophysics Data System (ADS)

    Kern, Christian; Kadic, Muamer; Wegener, Martin

    2017-01-01

    Effectively inverting the sign of material parameters is a striking possibility arising from the concept of metamaterials. Here, we show that the electrical properties of a p -type semiconductor can be mimicked by a metamaterial solely made of an n -type semiconductor. By fabricating and characterizing three-dimensional simple-cubic microlattices composed of interlocked hollow semiconducting tori, we demonstrate that sign and magnitude of the effective metamaterial Hall coefficient can be adjusted via a tori separation parameter—in agreement with previous theoretical and numerical predictions.

  6. Role of Fe and sign reversal of the Hall coefficient in quasicrystalline Al-Cu-Fe

    NASA Astrophysics Data System (ADS)

    Lindqvist, P.; Berger, C.; Klein, T.; Lanco, P.; Cyrot-Lackmann, F.; Calvayrac, Y.

    1993-07-01

    Electronic transport properties were measured for the stable icosahedral phase of Al-Cu-Fe for a large number of high-structural-quality samples of different compositions. At low temperature, the Hall coefficient RH and the conductivity σ are found to best correlate with the Fe content rather than with the electron per atom parameter which is usually used; RH changes sign at a concentration of 12.5 at. % Fe, where σ is at minimum. RH has a strong temperature dependence and can change sign with temperature. These features put the focus on the Fe d states and can be interpreted by a Hume-Rothery type of behavior including the sp-d hybridization effects.

  7. Reversible Brain Abnormalities in People Without Signs of Mountain Sickness During High-Altitude Exposure

    PubMed Central

    Fan, Cunxiu; Zhao, Yuhua; Yu, Qian; Yin, Wu; Liu, Haipeng; Lin, Jianzhong; Yang, Tianhe; Fan, Ming; Gesang, Luobu; Zhang, Jiaxing

    2016-01-01

    A large proportion of lowlanders ascending to high-altitude (HA) show no signs of mountain sickness. Whether their brains have indeed suffered from HA environment and the persistent sequelae after return to lowland remain unknown. Thirty-one sea-level college students, who had a 30-day teaching on Qinghai-Tibet plateau underwent MRI scans before, during, and two months after HA exposure. Brain volume, cortical structures, and white matter microstructure were measured. Besides, serum neuron-specific enolase (NSE), C-reactive protein, and interleukin-6 and neuropsychiatric behaviors were tested. After 30-day HA exposure, the gray and white matter volumes and cortical surface areas significantly increased, with cortical thicknesses and curvatures changed in a wide spread regions; Anisotropy decreased with diffusivities increased in multiple sites of white matter tracts. Two months after HA exposure, cortical measurements returned to basal level. However, increased anisotropy with decreased diffusivities was observed. Behaviors and serum inflammatory factor did not significant changed during three time-point tests. NSE significantly decreased during HA but increased after HA exposure. Results suggest brain swelling occurred in people without neurological signs at HA, but no negative sequelae in cortical structures and neuropsychiatric functions were left after the return to lowlands. Reoxygenation changed white matter microstructure. PMID:27633944

  8. Sign-reversal of the in-plane resistivity anisotropy in hole-doped iron pnictides

    NASA Astrophysics Data System (ADS)

    Blomberg, E. C.; Tanatar, M. A.; Fernandes, R. M.; Mazin, I. I.; Shen, Bing; Wen, Hai-Hu; Johannes, M. D.; Schmalian, J.; Prozorov, R.

    2013-05-01

    Unconventional superconductivity usually originates from several strongly coupled degrees of freedom, such as magnetic, charge and elastic. A highly anisotropic electronic phase, not driven by lattice degrees of freedom, has been proposed in some of these superconductors, from cuprates to iron-based compounds. In the iron pnictide BaFe2As2, this nematic phase arises in the paramagnetic phase and is present for wide doping and temperature ranges. Here we probe the in-plane electronic anisotropy of electron- and hole-doped BaFe2As2 compounds. Unlike other materials, the resistivity anisotropy behaves very differently for electron- and hole-type dopants and even changes sign on the hole-doped side. This behaviour is explained by Fermi surface reconstruction in the magnetic phase and spin-fluctuation scattering in the paramagnetic phase. This unique transport anisotropy unveils the primary role played by magnetic scattering, demonstrating the close connection between magnetism, nematicity and unconventional superconductivity.

  9. Sign-reversal of the in-plane resistivity anisotropy in hole-doped iron pnictides.

    PubMed

    Blomberg, E C; Tanatar, M A; Fernandes, R M; Mazin, I I; Shen, Bing; Wen, Hai-Hu; Johannes, M D; Schmalian, J; Prozorov, R

    2013-01-01

    Unconventional superconductivity usually originates from several strongly coupled degrees of freedom, such as magnetic, charge and elastic. A highly anisotropic electronic phase, not driven by lattice degrees of freedom, has been proposed in some of these superconductors, from cuprates to iron-based compounds. In the iron pnictide BaFe2As2, this nematic phase arises in the paramagnetic phase and is present for wide doping and temperature ranges. Here we probe the in-plane electronic anisotropy of electron- and hole-doped BaFe2As2 compounds. Unlike other materials, the resistivity anisotropy behaves very differently for electron- and hole-type dopants and even changes sign on the hole-doped side. This behaviour is explained by Fermi surface reconstruction in the magnetic phase and spin-fluctuation scattering in the paramagnetic phase. This unique transport anisotropy unveils the primary role played by magnetic scattering, demonstrating the close connection between magnetism, nematicity and unconventional superconductivity.

  10. Hepatic encephalopathy with reversible focal neurologic signs resembling acute stroke: case report.

    PubMed

    Yamamoto, Yoshiya; Nishiyama, Yasuhiro; Katsura, Ken-Ichiro; Yamazaki, Mineo; Katayama, Yasuo

    2011-01-01

    A 64-year-old female with a history of primary biliary cirrhosis and esophageal varices starting at age 39 was brought to our Stroke Care Unit by ambulance with right-side weakness and speech difficulty. Physical examination revealed right hemiparesis (including the face), sensory disturbances, pathological reflexes, and slightly decreased consciousness, with a Glasgow Coma Scale rating of E3V4M6. Flapping tremors and speech disturbance, as well as anarithmia, construction apraxia, and ideomotor apraxia, were noted, and her National Institutes of Health Stroke Scale score was 13. Initially, the patient was diagnosed with acute stroke and treated accordingly; however, subsequent findings from clinical images and electroencephalography led to a diagnosis of focal neurologic signs due to hepatic encephalopathy (HE). The patient had significantly reduced cerebral blood flow in the left side of the brain, probably due to microsurgical repair of an aneurysm done 2 years earlier. HE with exaggerated chronic liver damage might have made the previously silent ischemia clinically apparent. This interpretation is supported by the fact that the patient's neurologic deficits resolved once HE was adequately controlled. This case illustrates the need for careful assessment of background pathophysiology when diagnosing patients with stroke-like symptoms.

  11. Sign reversal of transformation entropy change in Co{sub 2}Cr(Ga,Si) shape memory alloys

    SciTech Connect

    Xu, Xiao Omori, Toshihiro; Kainuma, Ryosuke; Nagasako, Makoto; Kanomata, Takeshi

    2015-11-02

    In situ X-ray diffraction (XRD) measurements and compression tests were performed on Co{sub 2}Cr(Ga,Si) shape memory alloys. The reentrant martensitic transformation behavior was directly observed during the in situ XRD measurements. The high-temperature parent phase and low-temperature reentrant parent phase were found to have a continuous temperature dependence of lattice parameter, therefore suggesting that they are the same phase in nature. Moreover, compression tests were performed on a parent-phase single crystal sample; an evolution from normal to inverse temperature dependence of critical stress for martensitic transformation was directly observed. Based on the Clausius-Clapeyron analysis, a sign reversal of entropy change can be expected on the same alloy.

  12. First Detection of Sign-reversed Linear Polarization from the Forbidden [O I] 630.03 nm Line

    NASA Astrophysics Data System (ADS)

    de Wijn, A. G.; Socas-Navarro, H.; Vitas, N.

    2017-02-01

    We report on the detection of linear polarization of the forbidden [O i] 630.03 nm spectral line. The observations were carried out in the broader context of the determination of the solar oxygen abundance, an important problem in astrophysics that still remains unresolved. We obtained spectro-polarimetric data of the forbidden [O i] line at 630.03 nm as well as other neighboring permitted lines with the Solar Optical Telescope of the Hinode satellite. A novel averaging technique was used, yielding very high signal-to-noise ratios in excess of 105. We confirm that the linear polarization is sign-reversed compared to permitted lines as a result of the line being dominated by a magnetic dipole transition. Our observations open a new window for solar oxygen abundance studies, offering an alternative method to disentangle the Ni i blend from the [O i] line at 630.03 nm that has the advantage of simple LTE formation physics.

  13. An Unusual Lunar Halo

    ERIC Educational Resources Information Center

    Cardon, Bartley L.

    1977-01-01

    Discusses a photograph of an unusual combination of lunar halos: the 22-degree refraction halo, the circumscribed halo, and a reflection halo. Deduces the form and orientations of the ice crystals responsible for the observed halo features. (MLH)

  14. An Unusual Lunar Halo

    ERIC Educational Resources Information Center

    Cardon, Bartley L.

    1977-01-01

    Discusses a photograph of an unusual combination of lunar halos: the 22-degree refraction halo, the circumscribed halo, and a reflection halo. Deduces the form and orientations of the ice crystals responsible for the observed halo features. (MLH)

  15. ``A red cross appeared in the sky'' and other celestial signs: Presumable European aurorae in the mid AD 770s were halo displays

    NASA Astrophysics Data System (ADS)

    Neuhäuser, D. L.; Neuhäuser, R.

    2015-12-01

    The interpretation of the strong 14C variation around AD 775 as one (or several) solar super-flare(s) by, e.g., Usoskin et al. (2013) is based on alleged aurora sightings in the mid AD 770s in Europe: A red cross/crucifix in AD 773/4/6 from the Anglo-Saxon Chronicle, inflamed shields in AD 776 (both listed in the aurora catalogue of Link 1962), and riders on white horses in AD 773 (newly proposed as aurora in Usoskin et al. 2013), the two latter from the Royal Frankish Annals. We discuss the reports about these three sightings in detail here. We can show that all three can be interpreted convincingly as halo displays: The red cross or crucifix is formed by the horizontal arc and a vertical pillar of light (either with the Sun during sunset or with the moon after sunset); the inflamed shields and the riders on white horses were both two mock suns, especially the latter narrated in form of a Christian adaptation of the antique dioscuri motive. While the latter event took place early in AD 774 (dated AD 773 in Usoskin et al. 2013), the two other sightings have to be dated AD 776, i.e. anyway too late for being in connection with a 14C rise that started before AD 775. We also sketch the ideological background of those sightings and there were many similar reports throughout that time. In addition, we present a small drawing of a lunar halo display with horizontal arc and vertical pillar forming a cross for shortly later, namely AD 806 June 4, the night of full moon, also from the Anglo-Saxon Chronicle; we also show historic observations of halo phenomena (mock suns and crosses) from G. Kirch and Hevelius - and a modern photograph.

  16. Reliability of the hypernephroma halo

    SciTech Connect

    Wong, W.S.; Cochran, S.T.; Waisman, J.

    1981-11-01

    The excretory urograms and renal arteriograms of 68 patients with renal adenocarcinoma and 84 patients with renal masses other than renal adenocarcinoma were reviewed. The radiographs were examined for the presence or absence of the ''hypernephroma halo.'' The sensitivity of this sign was observed to be only 6% and 35% on excretory urography and arteriography, respectively. The specificity was 92% and 77%. However, the overall accuracy for this sign was only 54% and 59%. The relation between the halo and its postulated structural correlate, the tumor capsule, was also examined. There was no significant association demonstrable. It was concluded that the hypernephroma halo is not a reliable sign for diagnosing renal adenocarcinoma and that it probably does not represent the tumor capsule.

  17. Nuclear Halos

    SciTech Connect

    Vogt, Erich

    2010-07-27

    We show that extreme nuclear halos are caused only by pairs of s-wave neutrons (or single s-wave neutrons) and that such states occur much more frequently in the periodic table than previously believed. Besides lingering long near zero neutron separation energy such extreme halos have very remarkable properties: they can contribute significantly to the nuclear density at more than twice the normal nuclear radius and their spreading width can be very narrow. The properties of these states are primarily determined by the ''thickness'' of the nuclear surface in the mean-free nuclear potential and thus their importance increases greatly as we approach the neutron drip line. We discuss what such extreme halos are, where they occur, what their properties are and some of their impact on nuclear observations.

  18. Sign-a-Palooza

    ERIC Educational Resources Information Center

    McMorran, Charles; Reynolds, Veronica

    2010-01-01

    A halo of signs, some stuffed into thick plastic sheaths while others curled under yellow tape, cluttered the service desks of the New City Library. They bleated out messages of closings, procedures, and warnings. Their number undermined their cause. All too often a customer would ask a question that was answered by the very sign they had pushed…

  19. Sign-a-Palooza

    ERIC Educational Resources Information Center

    McMorran, Charles; Reynolds, Veronica

    2010-01-01

    A halo of signs, some stuffed into thick plastic sheaths while others curled under yellow tape, cluttered the service desks of the New City Library. They bleated out messages of closings, procedures, and warnings. Their number undermined their cause. All too often a customer would ask a question that was answered by the very sign they had pushed…

  20. Galaxy and Mass Assembly (GAMA): halo formation times and halo assembly bias on the cosmic web

    NASA Astrophysics Data System (ADS)

    Tojeiro, Rita; Eardley, Elizabeth; Peacock, John A.; Norberg, Peder; Alpaslan, Mehmet; Driver, Simon P.; Henriques, Bruno; Hopkins, Andrew M.; Kafle, Prajwal R.; Robotham, Aaron S. G.; Thomas, Peter; Tonini, Chiara; Wild, Vivienne

    2017-09-01

    We present evidence for halo assembly bias as a function of geometric environment (GE). By classifying Galaxy and Mass Assembly (GAMA) galaxy groups as residing in voids, sheets, filaments or knots using a tidal tensor method, we find that low-mass haloes that reside in knots are older than haloes of the same mass that reside in voids. This result provides direct support to theories that link strong halo tidal interactions with halo assembly times. The trend with GE is reversed at large halo mass, with haloes in knots being younger than haloes of the same mass in voids. We find a clear signal of halo downsizing - more massive haloes host galaxies that assembled their stars earlier. This overall trend holds independently of GE. We support our analysis with an in-depth exploration of the L-Galaxies semi-analytic model, used here to correlate several galaxy properties with three different definitions of halo formation time. We find a complex relationship between halo formation time and galaxy properties, with significant scatter. We confirm that stellar mass to halo mass ratio, specific star formation rate (SFR) and mass-weighed age are reasonable proxies of halo formation time, especially at low halo masses. Instantaneous SFR is a poor indicator at all halo masses. Using the same semi-analytic model, we create mock spectral observations using complex star formation and chemical enrichment histories, which approximately mimic GAMA's typical signal-to-noise ratio and wavelength range. We use these mocks to assert how well potential proxies of halo formation time may be recovered from GAMA-like spectroscopic data.

  1. Detection of canine distemper virus by reverse transcriptase-polymerase chain reaction in the urine of dogs with clinical signs of distemper encephalitis.

    PubMed

    Saito, T B; Alfieri, A A; Wosiacki, S R; Negrão, F J; Morais, H S A; Alfieri, A F

    2006-02-01

    In a prospective study we evaluated the use of the reverse transcriptase-polymerase chain reaction (RT-PCR) in urine samples to diagnose canine distemper virus in dogs with progressive neurological disease. A fragment of the nucleoprotein gene of canine distemper virus was amplified from the urine of 22 distemper dogs. The body fluids and leukocytes of 12 asymptomatic dogs were RT-PCR negative. RT-PCR of urine samples was more sensitive than serum and leukocytes and at least as sensitive as cerebrospinal fluid to screen for distemper in dogs with neurological signs and extraneural systemic signs.

  2. Sign-Reversing Orbital Polarization in the Nematic Phase of FeSe due to the C_{2} Symmetry Breaking in the Self-Energy.

    PubMed

    Onari, Seiichiro; Yamakawa, Youichi; Kontani, Hiroshi

    2016-06-03

    To understand the nematicity in Fe-based superconductors, nontrivial k dependence of the orbital polarization [ΔE_{xz}(k), ΔE_{yz}(k)] in the nematic phase, such as the sign reversal of the orbital splitting between Γ and X, Y points in FeSe, provides significant information. To solve this problem, we study the spontaneous symmetry breaking with respect to the orbital polarization and spin susceptibility self-consistently. In FeSe, due to the sign-reversing orbital order, the hole and electron pockets are elongated along the k_{y} and k_{x} axes, respectively, consistently with experiments. In addition, an electron pocket splits into two Dirac cone Fermi pockets while increasing the orbital polarization. The orbital order in Fe-based superconductors originates from the strong positive feedback between the nematic orbital order and spin susceptibility.

  3. Cobalamin deficiency manifested with seizures, mood oscillations, psychotic features and reversible dementia in the absence of typical neurologic and hematologic signs and symptoms: a case report.

    PubMed

    Vilibić, Maja; Jukić, Vlado; Vidović, Andelko; Brecić, Petrana

    2013-03-01

    Cobalamin deficiency is associated with a wide spectrum of hematologic, neurologic, gastroenterologic and psychiatric disorders or symptoms. We report a case of a 50-year-old man with complex partial seizures with secondary generalization, mood oscillations and psychotic symptoms alternating with confusion and reversible dementia secondary to cobalamin deficiency in the absence of typical neurologic and/or hematologic symptoms and signs. Exclusion of epilepsy, acute, atrophic or expansive lesion of central nervous system and usual etiology associated with reversible dementia (infectious diseases, an endocrine etiology and deficiency of vitamins other than cobalamin); finding of cobalamin deficiency only and complete neuropsychiatric recovery after substitution, confirmed etiology. Typical and atypical psychiatric manifestations due to cobalamin deficiency that precede neurologic and/or hematologic signs and symptoms can recover completely after adequate replacement therapy.

  4. Correlation between reversion of signs of the electric field in the near-cathode plasma and anode fall potential in a short DC glow discharge

    NASA Astrophysics Data System (ADS)

    Prokhorova, E. I.; Kudryavtsev, A. A.; Platonov, A. A.; Slyshov, A. G.

    2017-07-01

    Relatively simple probe and optical experiments were performed, confirming the presence of two main scenarios for the formation of the longitudinal characteristics of a short (without positive column) glow discharge. 1. At low pressures, when there is a single point of sign reverse of the electric field at the maximum of the plasma density, the anode fall is negative and the magnitude of the anode fall is small, there is no ionization and the anode area is dark. 2. Upon an increase in pressure, two points of field reversal are to be expected, the sign of the anode fall is positive and the anode fall of potential is comparable to the gas ionization potential; therefore, the intensive ionization directly at the anode, which glows brightly, takes place.

  5. Electrically sign-reversible transverse g -factors of holes in droplet epitaxial GaAs/AlGaAs quantum dots under uniaxial stress

    NASA Astrophysics Data System (ADS)

    Wu, Yu-Nien; Wu, Ming-Fan; Ou, Ya-Wen; Chou, Ying-Lin; Cheng, Shun-Jen

    2017-08-01

    We present a theoretical investigation of anisotropic g -factor tensors of single holes confined in droplet epitaxial GaAs/AlGaAs quantum dots under electrical and mechanical controls using the gauge-invariant discretization method within the framework of four-band Luttinger-Kohn k ⃗.p ⃗ theory. We reveal an intrinsic obstacle to realize the electrical sign reversal of the hole g -factors, being a key condition required for a full spin control in the scheme of g -tensor modulation, for the quantum dots solely with electrical bias control. Constructively, our studies show that, besides electrical gating, slightly stressing an inherently unstrained droplet epitaxial GaAs/AlGaAs quantum dot can offset the transverse hole g -factor to be nearly zero and make the electrical sign reversal of the hole g -factors feasible.

  6. Reversing the sign of the spin-polarized current across a Fe/GaAs tunnel barrier at finite voltage bias

    NASA Astrophysics Data System (ADS)

    Crooker, S. A.; Lou, X.; Adelmann, C.; Garlid, E. S.; Zhang, J.; Reddy, S. M.; Flexner, S. D.; Palmstrom, C. J.; Crowell, P. A.

    2007-03-01

    As a function of the voltage bias across a Fe/GaAs Schottky tunnel barrier, we measure the sign and magnitude of the electrically-injected electron spin polarization in the semiconductor, PGaAs, using magneto-optical Kerr rotation at 10 K. Both images and Hanle depolarization curves reveal that the sign of PGaAs inverts when sweeping from small reverse bias (electrons flowing into GaAs) to small forward bias (electrons flowing into Fe), as expected from linear response. More strikingly, PGaAs inverts sign again at higher bias across the Fe/GaAs barrier. This crossover bias (|Vcross| < 0.1 V in the structures studied) is sample-dependent, and can occur under either forward- or reverse-bias conditions, depending on sample. These data concur with all-electrical measurements of PGaAs in lateral spin transport devices having a source, drain, and a third `non-local' detection electrode. Models to describe these data will be discussed. We further show that, when Fe/GaAs tunnel barriers are employed as electrical spin detectors, both the sign and magnitude of the detection sensitivity can be tuned with applied bias on the detector. This work is supported by the Los Alamos LDRD and NSF MRSEC programs, and ONR.

  7. Sign reversal of magnetization and tunable exchange bias field in NdCr1-xFexO3 (x=0.05-0.2)

    NASA Astrophysics Data System (ADS)

    Bora, Tribedi; Ravi, S.

    2015-07-01

    Magnetization reversal and tunable exchange bias behavior are observed in NdCr1-xFexO3 compounds for x=0.05-0.20. The magnetic compensation temperature (Tcomp) is found to increase with increase in Fe concentration and its maximum value is 198 K for x=0.15 sample. The observed magnetization reversal is explained by considering the competition between the weak ferromagnetic component of Cr3+ ions and the paramagnetic moments of Nd3+ and Fe3+ ions under the influence of negative internal magnetic field. The exchange anisotropy between the above two components of magnetic moments give rise to tunable positive and negative exchange bias fields. The sign reversal of exchange bias field also coincides with Tcomp. Bipolar switching of magnetization is demonstrated at T

  8. The prodigious halo of the other Huygens.

    PubMed

    Können, Gunther P

    2015-02-01

    At the height of the ceremony in the Principality of Orange of the restoration of the sovereignty of the House of Nassau in 1665, a ceremony led by Christiaan's father, Constantijn Huygens, a "solar crown" appeared in the sky, apparently a divine sign of approval. A nearly forgotten contemporary color engraving of this miraculous event has survived. Constantijn seized the opportunity by using to his advantage the general euphoria among the citizens caused by the appearance. We argue that Constantijn knew exactly what was going on in the sky because of his son's work on halo theory. Given its brightness and its time of appearance, it seems plausible that the most prominent halo in the Orange halo display was a circumscribed halo rather than the more familiar but bleaker circular 22° halo. The same probably holds for most of the other high-sun halos that caused general consternation, dating from the Octavian halo of 44 BC, to the Chernobyl halo of 1986, and indeed up to bright high-sun halos of the present.

  9. Reversals.

    ERIC Educational Resources Information Center

    National Center on Educational Media and Materials for the Handicapped, Columbus, OH.

    Selected from the National Instructional Materials Information System (NIMIS)--a computer based on-line interactive retrieval system on special education materials--the bibliography covers nine materials for remediating reversals in handicapped students at the early childhood and elementary levels. Entries are presented in order of NIMIS accession…

  10. Unique combination of hyperintense vessel sign on initial FLAIR and delayed vasoconstriction on MRA in reversible cerebral vasoconstriction syndrome: a case report.

    PubMed

    Kameda, Tomoaki; Namekawa, Michito; Shimazaki, Haruo; Minakata, Daisuke; Matsuura, Tohru; Nakano, Imaharu

    2014-11-01

    Reversible cerebral vasoconstriction syndrome is characterized by thunderclap headache and reversible cerebral vasoconstriction on angiographic findings. It can be difficult to diagnose when initial angiography is normal. A 30-year-old woman was admitted because of sudden-onset thunderclap headache and seizure on postpartum day 7. Brain MRI on fluid-attenuated inversion recovery (FLAIR) showed hyperintense vessel sign (HVS), which usually means slow flow due to severe proximal arterial stenosis. However, magnetic resonance angiography (MRA) indicated that proximal arteries was normal. After nicardipine treatment, her symptoms improved dramatically. Follow-up FLAIR on day 7 showed complete resolution of HVS, while a series of MRAs revealed reversible multifocal segmental vasoconstriction. HVS on initial FLAIR is useful for an early diagnosis of reversible cerebral vasoconstriction syndrome. As the delayed vasoconstriction on MRA can be observed, reversible cerebral vasoconstriction syndrome may progress from distal small to proximal larger arteries. © International Headache Society 2014 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.

  11. Halo-free Phase Contrast Microscopy

    PubMed Central

    Nguyen, Tan H.; Kandel, Mikhail; Shakir, Haadi M.; Best-Popescu, Catherine; Arikkath, Jyothi; Do, Minh N.; Popescu, Gabriel

    2017-01-01

    We present a new approach for retrieving halo-free phase contrast microscopy (hfPC) images by upgrading the conventional PC microscope with an external interferometric module, which generates sufficient data for reversing the halo artifact. Acquiring four independent intensity images, our approach first measures haloed phase maps of the sample. We solve for the halo-free sample transmission function by using a physical model of the image formation under partial spatial coherence. Using this halo-free sample transmission, we can numerically generate artifact-free PC images. Furthermore, this transmission can be further used to obtain quantitative information about the sample, e.g., the thickness with known refractive indices, dry mass of live cells during their cycles. We tested our hfPC method on various control samples, e.g., beads, pillars and validated its potential for biological investigation by imaging live HeLa cells, red blood cells, and neurons. PMID:28338086

  12. Halo-free Phase Contrast Microscopy.

    PubMed

    Nguyen, Tan H; Kandel, Mikhail; Shakir, Haadi M; Best-Popescu, Catherine; Arikkath, Jyothi; Do, Minh N; Popescu, Gabriel

    2017-03-24

    We present a new approach for retrieving halo-free phase contrast microscopy (hfPC) images by upgrading the conventional PC microscope with an external interferometric module, which generates sufficient data for reversing the halo artifact. Acquiring four independent intensity images, our approach first measures haloed phase maps of the sample. We solve for the halo-free sample transmission function by using a physical model of the image formation under partial spatial coherence. Using this halo-free sample transmission, we can numerically generate artifact-free PC images. Furthermore, this transmission can be further used to obtain quantitative information about the sample, e.g., the thickness with known refractive indices, dry mass of live cells during their cycles. We tested our hfPC method on various control samples, e.g., beads, pillars and validated its potential for biological investigation by imaging live HeLa cells, red blood cells, and neurons.

  13. Halo-free Phase Contrast Microscopy

    NASA Astrophysics Data System (ADS)

    Nguyen, Tan H.; Kandel, Mikhail; Shakir, Haadi M.; Best-Popescu, Catherine; Arikkath, Jyothi; Do, Minh N.; Popescu, Gabriel

    2017-03-01

    We present a new approach for retrieving halo-free phase contrast microscopy (hfPC) images by upgrading the conventional PC microscope with an external interferometric module, which generates sufficient data for reversing the halo artifact. Acquiring four independent intensity images, our approach first measures haloed phase maps of the sample. We solve for the halo-free sample transmission function by using a physical model of the image formation under partial spatial coherence. Using this halo-free sample transmission, we can numerically generate artifact-free PC images. Furthermore, this transmission can be further used to obtain quantitative information about the sample, e.g., the thickness with known refractive indices, dry mass of live cells during their cycles. We tested our hfPC method on various control samples, e.g., beads, pillars and validated its potential for biological investigation by imaging live HeLa cells, red blood cells, and neurons.

  14. Borromean halo, Tango halo, and halo isomers in atomic nuclei

    NASA Astrophysics Data System (ADS)

    Izosimov, Igor

    2016-01-01

    Structure of the ground and excited states in halo-like nuclei is discussed. Both the Borromean and tango halo types can be observed for n-p configurations of atomic nuclei.Structure of the halo may be different for the different levels and resonances in atomic nuclei. Isobar analog, double isobar analog, configuration, and double configuration states can simultaneously have n-n, n-p, and p-p halo components in their wave functions. When the halo structure of the excited state differs from that of the ground state, or the ground state has non-halo structure, the γ-transition from the excited state to the ground state can be essentially hindered, i.e. the formation of a specific type of isomers (halo isomers) becomes possible. B(Mγ) and B(Eγ) values for γ-transitions in 6,7,8Li, 8,9,10Be, 8,10,11B, 10,11,12,13,14C, 13,14,15,16,17N, 15,16,17,19O, and 17F are analyzed. Special attention is given to nuclei which ground state does not exhibit halo structure but the excited state (halo isomer) may have one.

  15. The Halo

    NASA Image and Video Library

    2013-12-23

    NASA's Cassini spacecraft looks towards the dark side of Saturn's largest moon, Titan, capturing the blue halo caused by a haze layer that hovers high in the moon's atmosphere. The haze that permeates Titan's atmosphere scatters sunlight and produces the orange color seen here. More on Titan's orange and blue hazes can be found at PIA14913. This view looks towards the side of Titan (3,200 miles or 5,150 kilometers across) that leads in its orbit around Saturn. North on Titan is up and rotated 40 degrees to the left. Images taken using red, green and blue spectral filters were combined to create this natural-color view. The images were taken with the Cassini spacecraft narrow-angle camera on Nov. 3, 2013. The view was acquired at a distance of approximately 2.421 million miles (3.896 million kilometers) from Titan. Image scale is 14 miles (23 kilometers) per pixel. http://photojournal.jpl.nasa.gov/catalog/PIA17180

  16. Sign reversal of magnetization and exchange bias in Ni(Cr1-xAlx)2O4 (x=0-0.50)

    NASA Astrophysics Data System (ADS)

    Barman, Junmoni; Ravi, S.

    2017-03-01

    Ni(Cr1-xAlx)2O4 (x=0-0.50) samples were prepared in single phase form by using sol-gel method and their structural and magnetic properties were studied. Al substitution transforms the crystal structure of NiCr2O4 from tetragonal cell with space group I41/amd to cubic cell of Fd 3 barm space group. Magnetization measurements by varying the temperature and magnetic field were carried out to investigate the interesting magnetization reversal and exchange bias behaviors. Magnetization reversal is observed for x=0.10 sample with a magnetic compensation temperature of 40 K and it is explained by considering different temperature dependences of magnetic moments of the two sublattices. Shifting of magnetic hysteresis loops towards the negative magnetic field axis and hence the presence of negative exchange bias field is observed for x=0.15 sample. The x=0.10 sample exhibits the tunable positive and negative exchange bias field. Exchange bias in these samples is explained considering the anisotropic exchange interaction between the ferrimagnetic and the antiferromagnetic components of magnetic spins. However, the sign reversal of exchange bias field is due to the change in domination of one ferrimagnetic sublattice over the other with variation in temperature. Both normal and inverse magnetocaloric effects are observed for x=0.10 sample.

  17. A ''LIGHT'', CENTRALLY CONCENTRATED MILKY WAY HALO?

    SciTech Connect

    Rashkov, Valery; Pillepich, Annalisa; Deason, Alis J.; Madau, Piero; Rockosi, Constance M.; Mayer, Lucio

    2013-08-20

    We discuss a novel approach to ''weighing'' the Milky Way (MW) dark matter halo, one that combines the latest samples of halo stars selected from the Sloan Digital Sky Survey (SDSS) with state of the art numerical simulations of MW analogs. The fully cosmological runs employed in the present study include ''Eris'', one of the highest resolution hydrodynamical simulations of the formation of a M{sub vir} = 8 Multiplication-Sign 10{sup 11} M{sub Sun} late-type spiral, and the dark-matter-only M{sub vir} = 1.7 Multiplication-Sign 10{sup 12} M{sub Sun} ''Via Lactea II'' (VLII) simulation. Eris provides an excellent laboratory for creating mock SDSS samples of tracer halo stars, and we successfully compare their density, velocity anisotropy, and radial velocity dispersion profiles with the observational data. Most mock SDSS realizations show the same ''cold veil'' recently observed in the distant stellar halo of the MW, with tracers as cold as {sigma}{sub los} Almost-Equal-To 50 km s{sup -1} between 100 and 150 kpc. Controlled experiments based on the integration of the spherical Jeans equation as well as a particle tagging technique applied to VLII show that a ''heavy'' M{sub vir} Almost-Equal-To 2 Multiplication-Sign 10{sup 12} M{sub Sun} realistic host produces a poor fit to the kinematic SDSS data. We argue that these results offer added evidence for a ''light'', centrally concentrated MW halo.

  18. "Invisible" Galactic Halos.

    ERIC Educational Resources Information Center

    Lugt, Karel Vander

    1993-01-01

    Develops a simple core-halo model of a galaxy that exhibits the main features of observed rotation curves and quantitatively illustrates the need to postulate halos of dark matter. Uses only elementary mechanics. (Author/MVL)

  19. "Invisible" Galactic Halos.

    ERIC Educational Resources Information Center

    Lugt, Karel Vander

    1993-01-01

    Develops a simple core-halo model of a galaxy that exhibits the main features of observed rotation curves and quantitatively illustrates the need to postulate halos of dark matter. Uses only elementary mechanics. (Author/MVL)

  20. Halo CME

    NASA Image and Video Library

    2017-09-28

    A giant cloud appears to expand outward from the sun in all directions in this image from Sept. 28, 2012, which is called a halo CME. This kind of image occurs when a CME moves toward Earth – as here – or directly away from it. Credit: ESA/NASA/SOHO CME WEEK: What To See in CME Images Two main types of explosions occur on the sun: solar flares and coronal mass ejections. Unlike the energy and x-rays produced in a solar flare – which can reach Earth at the speed of light in eight minutes – coronal mass ejections are giant, expanding clouds of solar material that take one to three days to reach Earth. Once at Earth, these ejections, also called CMEs, can impact satellites in space or interfere with radio communications. During CME WEEK from Sept. 22 to 26, 2014, we explore different aspects of these giant eruptions that surge out from the star we live with. When a coronal mass ejection blasts off the sun, scientists rely on instruments called coronagraphs to track their progress. Coronagraphs block out the bright light of the sun, so that the much fainter material in the solar atmosphere -- including CMEs -- can be seen in the surrounding space. CMEs appear in these images as expanding shells of material from the sun's atmosphere -- sometimes a core of colder, solar material (called a filament) from near the sun's surface moves in the center. But mapping out such three-dimensional components from a two-dimensional image isn't easy. Watch the slideshow to find out how scientists interpret what they see in CME pictures. The images in the slideshow are from the three sets of coronagraphs NASA currently has in space. One is on the joint European Space Agency and NASA Solar and Heliospheric Observatory, or SOHO. SOHO launched in 1995, and sits between Earth and the sun about a million miles away from Earth. The other two coronagraphs are on the two spacecraft of the NASA Solar Terrestrial Relations Observatory, or STEREO, mission, which launched in 2006. The two

  1. Farside Halo

    NASA Image and Video Library

    2017-09-28

    There's no way to tell from this SOHO image whether the halo CME on March 5, 2013, originated from the front or far of the sun. But the STEREO spacecraft were watching the sun from the sides and showed it was from the far side. The bright planet is Venus. Credit: NASA/SOHO CME WEEK: What To See in CME Images Two main types of explosions occur on the sun: solar flares and coronal mass ejections. Unlike the energy and x-rays produced in a solar flare – which can reach Earth at the speed of light in eight minutes – coronal mass ejections are giant, expanding clouds of solar material that take one to three days to reach Earth. Once at Earth, these ejections, also called CMEs, can impact satellites in space or interfere with radio communications. During CME WEEK from Sept. 22 to 26, 2014, we explore different aspects of these giant eruptions that surge out from the star we live with. When a coronal mass ejection blasts off the sun, scientists rely on instruments called coronagraphs to track their progress. Coronagraphs block out the bright light of the sun, so that the much fainter material in the solar atmosphere -- including CMEs -- can be seen in the surrounding space. CMEs appear in these images as expanding shells of material from the sun's atmosphere -- sometimes a core of colder, solar material (called a filament) from near the sun's surface moves in the center. But mapping out such three-dimensional components from a two-dimensional image isn't easy. Watch the slideshow to find out how scientists interpret what they see in CME pictures. The images in the slideshow are from the three sets of coronagraphs NASA currently has in space. One is on the joint European Space Agency and NASA Solar and Heliospheric Observatory, or SOHO. SOHO launched in 1995, and sits between Earth and the sun about a million miles away from Earth. The other two coronagraphs are on the two spacecraft of the NASA Solar Terrestrial Relations Observatory, or STEREO, mission, which

  2. Magnetic compensation phenomenon and the sign reversal in the exchange bias field in a single crystal of Nd0.75Ho0.25Al2

    NASA Astrophysics Data System (ADS)

    Kulkarni, P. D.; Thamizhavel, A.; Rakhecha, V. C.; Nigam, A. K.; Paulose, P. L.; Ramakrishnan, S.; Grover, A. K.

    2009-05-01

    In the Nd0.75Ho0.25Al2 alloy system, the magnetic moments of Nd and Ho occupying the same crystallographic site randomly are antiferromagnetically coupled via long-range indirect exchange interaction mediated by the conduction electrons. A single crystal grown at this stoichiometry displays a magnetic compensation behavior (Tcomp~24 K) in all orientations. In the close vicinity of Tcomp, the magnetization hysteresis loops measured for H || [100] assume an asymmetric shape, and the notion of an exchange bias field (Hexch) surfaces. Hexch changes sign across Tcomp as the left shift of the loops transforms to the right shift. This phase reversal appears to correlate with the corresponding reversal in the directions of the local magnetic moments of Nd3+ and Ho3+ ions together with that of the conduction electron polarization (CEP). Near Tcomp, where the opposing contributions to the net magnetization from local magnetic moments are nearly equal, the contribution from CEP assumes an accentuated significance. Interestingly, the width of the M-H loop shows a divergence, followed by a collapse on approaching Tcomp from high- as well as low-temperature ends. The observed behavior confirms a long-standing prediction based on a phenomenological model for ferrimagnetic systems. The field-induced changes in the magnetization data leave an imprint of a quasi-phase transition in the heat capacity data. Magneto-resistance (ΔR/R vs. T) has an oscillatory response, in which onset of magnetic ordering and phase reversal in magnetic orientations can be recognized.

  3. Resolved Stellar Halos of M87 and NGC 5128

    NASA Astrophysics Data System (ADS)

    Bird, Sarah A.; Harris, William; Flynn, Chris; Blakeslee, John P.; Valtonen, Mauri

    2015-08-01

    We search halo fields of two giant elliptical galaxies: M87, using HST images at 10 kpc from the center, and NGC 5128 (Cen A), using VIMOS VLT images at 65 kpc from the center and archival HST data from 8 to 38 kpc from the center. We resolve thousands of red-giant-branch stars in these stellar halo fields using V and I filters, and, in addition, measure the metallicity using stellar isochrones. In Cen A, we find that the density of metal-rich and metal-poor halo stars falls off with the same slope in the de Vaucouleurs' law profile, from the inner halo of 8 kpc out to 70 kpc, with no sign of a transition to dominance by metal-poor stars. We also find that the metallicity distribution of the inner stellar halo of M87 is most similar to that of NGC 5128's inner stellar halo.

  4. Design, Synthesis and Biological Evaluation of 1-[(2-benzyloxyl/alkoxyl) methyl]-5-halo-6-aryluracils as Potent HIV-1 Non-Nucleoside Reverse Transcriptase Inhibitors with Improved Drug Resistance Profile

    PubMed Central

    Wang, Xiaowei; Zhang, Jianfang; Huang, Yang; Wang, Ruiping; Zhang, Liang; Qiao, Kang; Li, Li; Liu, Chang; Ouyang, Yabo; Xu, Weisi; Zhang, Zhili; Zhang, Liangren; Shao, Yiming; Jiang, Shibo; Ma, Liying; Liu, Junyi

    2012-01-01

    Since the emergence of drug-resistant mutants has limited the efficacy of non-nucleoside reverse transcriptase inhibitors (NNRTIs), it is essential to develop new antivirals with better drug-resistance and pharmacokinetic profiles. Here we designed and synthesized a series of 1-[(2-benzyloxyl/alkoxyl)methyl]-5-halo-6-aryluracils, the HEPT analogues, and evaluated their biological activity using Nevirapine and 18 (TNK-651) as reference compounds. Most of these compounds, especially 6b, 7b, 9b, 11b and 7c, exhibited highly potent anti-HIV-1 activity against both wild-type and NNRTI-resistant HIV-1 strains. The compound 7b, that had the highest selectivity index (SI = 38,215), is more potent than Nevirapine and 18. These results suggest that introduction of halogen at the C-5 position may contribute to the effectiveness of these compounds against RTI-resistant variants. In addition, m-substituents on the C-6 aromatic moiety could significantly enhance activity against NNRTI-resistant HIV-1 strains. These compounds can be further developed as next-generation NNRTIs with improved antiviral efficacy and drug-resistance profile. PMID:22283377

  5. Dwarf Dark Matter Halos

    NASA Astrophysics Data System (ADS)

    Colín, P.; Klypin, A.; Valenzuela, O.; Gottlöber, Stefan

    2004-09-01

    We study properties of dark matter halos at high redshifts z=2-10 for a vast range of masses with the emphasis on dwarf halos with masses of 107-109 h-1 Msolar. We find that the density profiles of relaxed dwarf halos are well fitted by the Navarro, Frenk, & White (NFW) profile and do not have cores. We compute the halo mass function and the halo spin parameter distribution and find that the former is very well reproduced by the Sheth & Tormen model, while the latter is well fitted by a lognormal distribution with λ0=0.042 and σλ=0.63. We estimate the distribution of concentrations for halos in a mass range that covers 6 orders of magnitude, from 107 to 1013 h-1 Msolar, and find that the data are well reproduced by the model of Bullock et al. The extrapolation of our results to z=0 predicts that present-day isolated dwarf halos should have a very large median concentration of ~35. We measure the subhalo circular velocity functions for halos with masses that range from 4.6×109 to 1013 h-1 Msolar and find that they are similar when normalized to the circular velocity of the parent halo. Dwarf halos studied in this paper are many orders of magnitude smaller than well-studied cluster- and Milky Way-sized halos. Yet, in all respects the dwarfs are just downscaled versions of the large halos. They are cuspy and, as expected, more concentrated. They have the same spin parameter distribution and follow the same mass function that was measured for large halos.

  6. Sign reversal of the Hall effect below T sub c in untwinned single-crystal YBa sub 2 Cu sub 3 O sub 7 minus. delta

    SciTech Connect

    Rice, J.P.; Rigakis, N.; Ginsberg, D.M.; Mochel, J.M. Materials Research Laboratory, University of Illinois at Urbana-Champaign, 1110 West Green Street, Urbana, Illinois 61801 )

    1992-11-01

    Because of possible effects from (110) twin planes and {ital a}-{ital b} anisotropy in YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}}, measurements on untwinned crystals are desirable. We have measured the Hall effect and resistivity simultaneously in untwinned single-crystal YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} with a superconducting transition temperature {ital T}{sub {ital c}}=93 K, with the magnetic field along the {ital c} axis. Below {ital T}{sub {ital c}}, the measured Hall resistivity reverses sign, becoming negative over a range of temperature and magnetic field, and the location and magnitude of the minimum is similar to that measured previously by others on twinned samples. These results show that the negative Hall resistivity is not caused by twin planes inducing guided vortex motion or vortex pinning. In addition, the exponent characterizing a scaling relation of the longitudinal to the Hall resistivity has a value consistent with that measured on thin films.

  7. Halos around planetary nebulae

    NASA Technical Reports Server (NTRS)

    Jewitt, D. C.; Danielson, G. E.; Kupferman, P. N.

    1986-01-01

    Preliminary results of a CCD survey designed to detect and investigate faint halos around planetary nebulae are reported. A TI 800 x 800 pixel CCD was used to take deep exposures of 44 planetary nebulae. The exposures were obtained through an H-alpha filter at the Cassegrain focus of the Palomar 1.5 m telescope. Spatial resolutions of 1 to 2 arcsec were obtained across 400 arcsec wide fields. The images, which are in many cases considerably deeper than any previously taken, reveal numerous planetary nebula halos. About two-thirds of the studied nebulae possess extensive outer halos, here defined as any extended emission beyond the 10 percent isophote. Ionized sulphur electron density measurements show that in some nebulae, the mass in the halo is comparable to the mass contained in the primary H II region. The data have been used to place constraints on the mode of origin of the halos. It is likely that the halos originate either by dynamical separation of a single ejected shell of gas or by the ejection of two or more such shells from the central star. It is possible but less likely that the halos are caused by excitation of the preplanetary stellar wind and improbable that the halos represent reflection nebulae.

  8. THE HALO OCCUPATION DISTRIBUTION OF SDSS QUASARS

    SciTech Connect

    Richardson, Jonathan; Chatterjee, Suchetana; Nagai, Daisuke; Zheng Zheng; Shen Yue

    2012-08-10

    We present an estimate of the projected two-point correlation function (2PCF) of quasars in the Sloan Digital Sky Survey (SDSS) over the full range of one- and two-halo scales, 0.02 h{sup -1} Mpc < r{sub p} < 120 h{sup -1} Mpc. This was achieved by combining data from SDSS DR7 on large scales and Hennawi et al. (with appropriate statistical corrections) on small scales. Our combined clustering sample is the largest spectroscopic quasar clustering sample to date, containing {approx}48, 000 quasars in the redshift range 0.4 {approx}< z {approx}< 2.5 with median redshift 1.4. We interpret these precise 2PCF measurements within the halo occupation distribution (HOD) framework and constrain the occupation functions of central and satellite quasars in dark matter halos. In order to explain the small-scale clustering, the HOD modeling requires that a small fraction of z {approx} 1.4 quasars, f{sub sat} = (7.4 {+-} 1.4) Multiplication-Sign 10{sup -4}, be satellites in dark matter halos. At z {approx} 1.4, the median masses of the host halos of central and satellite quasars are constrained to be M{sub cen} = 4.1{sup +0.3}{sub -0.4} Multiplication-Sign 10{sup 12} h{sup -1} M{sub Sun} and M{sub sat} = 3.6{sup +0.8}{sub -1.0} Multiplication-Sign 10{sup 14} h{sup -1} M{sub Sun }, respectively. To investigate the redshift evolution of the quasar-halo relationship, we also perform HOD modeling of the projected 2PCF measured by Shen et al. for SDSS quasars with median redshift 3.2. We find tentative evidence for an increase in the mass scale of quasar host halos-the inferred median mass of halos hosting central quasars at z {approx} 3.2 is M{sub cen} = 14.1{sup +5.8}{sub -6.9} Multiplication-Sign 10{sup 12} h{sup -1} M{sub Sun }. The cutoff profiles of the mean occupation functions of central quasars reveal that quasar luminosity is more tightly correlated with halo mass at higher redshifts. The average quasar duty cycle around the median host halo mass is inferred to be f{sub q

  9. The halo fixator.

    PubMed

    Bono, Christopher M

    2007-12-01

    The halo fixator may be used for the definitive treatment of cervical spine trauma, preoperative reduction in the patient with spinal deformity, and adjunctive postoperative stabilization following cervical spine surgery. Halo fixation decreases cervical motion by 30% to 96%. Absolute contraindications include cranial fracture, infection, and severe soft-tissue injury at the proposed pin sites. Relative contraindications include severe chest trauma, obesity, advanced age, and a barrel-shaped chest. In children, a computed tomography scan of the head should be obtained before pin placement to determine cranial bone thickness. Complications of halo fixation include pin loosening, pin site infection, and skin breakdown. A concerning rate of life-threatening complications, such as respiratory distress, has been reported in elderly patients. Despite a paucity of contemporary data, recent retrospective studies have demonstrated acceptable results for halo fixation in managing some upper and lower cervical spine injuries.

  10. AHF: AMIGA'S HALO FINDER

    SciTech Connect

    Knollmann, Steffen R.; Knebe, Alexander

    2009-06-15

    Cosmological simulations are the key tool for investigating the different processes involved in the formation of the universe from small initial density perturbations to galaxies and clusters of galaxies observed today. The identification and analysis of bound objects, halos, is one of the most important steps in drawing useful physical information from simulations. In the advent of larger and larger simulations, a reliable and parallel halo finder, able to cope with the ever-increasing data files, is a must. In this work we present the freely available MPI parallel halo finder AHF. We provide a description of the algorithm and the strategy followed to handle large simulation data. We also describe the parameters a user may choose in order to influence the process of halo finding, as well as pointing out which parameters are crucial to ensure untainted results from the parallel approach. Furthermore, we demonstrate the ability of AHF to scale to high-resolution simulations.

  11. Halo vest instrumentation

    NASA Astrophysics Data System (ADS)

    Huston, Dryver R.; Krag, Martin

    1996-05-01

    The halo vest is a head and neck immobilization system that is often used on patients that are recovering from cervical trauma or surgery. The halo vest system consists of a rigid halo that is firmly attached to the skull, an upright support structure for stabilization and immobilization, and a torso-enveloping vest. The main purpose of this study was to measure the forces that are carried by the halo-vest structure as the subject undergoes various activities of daily living and external loading for different vest designs. A tethered strain gage load cell based instrumentation system was used to take these load measurements on ten different subjects. Three different halo-vest systems were evaluated. The primary difference between the vests was the amount of torso coverage and the use of shoulder straps. The loads were measured, analyzed and used to compare the vests and to create a model of halo-vest-neck mechanics. Future applications of this technology to standalone data logging, pin-load measuring and biofeedback applications are discussed.

  12. The HALO / HALO-2 Supernova Neutrino Detectors

    NASA Astrophysics Data System (ADS)

    Yen, Stanley; HALO Collaboration; HALO-2 Collaboration

    2016-09-01

    The Helium and Lead Observatory (HALO) is a dedicated supernova neutrino detector in SNOLAB, which is built from 79 tons of surplus lead and the helium-3 neutron detectors from the SNO experiment. It is sensitive primarily to electron neutrinos, and is thus complementary to water Cerenkov and organic scintillation detectors which are primarily sensitive to electron anti-neutrinos. A comparison of the rates in these complementary detectors will enable a flavor decomposition of the neutrino flux from the next galactic core-collapse supernova. We have tentative ideas to build a 1000-ton HALO-2 detector in the Gran Sasso laboratory by using the lead from the decommissioned OPERA detector. We are exploring several neutron detector technologies to supplement the existing helium-3 detectors. We welcome new collaborators to join us. This research is supported by the NRC and NSERC (Canada), the US DOE and NSF, and the German RISE program.

  13. Epicardial halo phenomenon: a guide for pericardiocentesis?

    PubMed

    Ristić, Arsen D; Wagner, Hans-Joachim; Maksimović, Ružica; Maisch, Bernhard

    2013-05-01

    The epicardial halo delineates the heart shadow in fluoroscopy. To establish whether the sign is applicable to pericardiocentesis guidance, three investigators evaluated its intensity as absent = grade 0, indistinct = 0.5, clear = 1, intensive = 2 in posterior-anterior (PA) and lateral fluoroscopies recorded before pericardiocentesis or cardiac catheterization (Philips Integris-II BH3000). Three populations were studied: (a) 32 patients with pericardial effusion (PE group), 53.1 % males, aged 53.9 ± 13.9 years; (b) 14 patients with perimyocarditis (PM group), 64.3 % males, aged 51.6 ± 14.4 years; and (c) 46 coronary patients (CAD group), no PE, 95.6 % males, aged 67.3 ± 11.8 years. The intensity of the halo phenomenon was highest in patients with PE, lowest in patients with CAD, and intermediate in patients with PM (median sum of grades in PA/lateral view: 4/5 vs. 2/2.5 vs. 3/3, respectively) (p < 0.01). The halo phenomenon correlated well with HR and echocardiographic PE size in both angiographic views. The correlation with body mass index (BMI) and age was significant only in the lateral view and with PE volume only in the PA view. The sensitivity of the halo sign for PE was 84.1 % in PA and 92.0 % in lateral views. In 10/32 PE patients, the evaluation of the sign was repeated after PE drainage, revealing lower grades both in PA and in lateral views (p < 0.01). In conclusion, the epicardial halo sign is highly sensitive for the detection of a PE; it correlates well in at least one angiographic projection with the PE volume, HR, age, BMI, and the PE size in echocardiography and could be therefore applied as a safety guide for pericardiocentesis.

  14. Historic halo displays as weather indicator: Criteria and examples

    NASA Astrophysics Data System (ADS)

    Neuhäuser, Dagmar L.; Neuhäuser, Ralph

    2016-04-01

    There are numerous celestial signs reported in historic records, many of them refer to atmospheric ("sub-lunar") phenomena, such as ice halos and aurorae. In an interdisciplinary collaboration between astrophysics and cultural astronomy, we noticed that celestial observations including meteorological phenomena are often misinterpreted, mostly due to missing genuine criteria: especially ice crystal halos were recorded frequently in past centuries for religious reasons, but are mistaken nowadays often for other phenomena like aurorae. Ice halo displays yield clear information on humidity and temperature in certain atmospheric layers, and thereby indicate certain weather patterns. Ancient so-called rain makers used halo observations for weather forecast; e.g., a connection between certain halo displays and rain a few day later is statistically significant. Ice halos exist around sun and moon and are reported for both (they can stay for several days): many near, middle, and far eastern records from day- and night-time include such observations with high frequency. (Partly based on publications on halos by D.L. Neuhäuser & R. Neuhäuser, available at http://www.astro.uni-jena.de/index.php/terra-astronomy.html)

  15. The Halos and Environments of Nearby Galaxies (HERON) Survey

    NASA Astrophysics Data System (ADS)

    Rich, R. Michael; Brosch, Noah; Bullock, James; Burkert, Andreas; Collins, Michelle; de Groot, Laura; Kennefick, Julia; Koch, Andreas; Longstaff, Francis; Sales, Laura

    2017-03-01

    We have used dedicated 0.7m telescopes in California and Israel to image the halos of ~ 200 galaxies in the Local Volume to 29 mag/sq arcsec, the sample mainly drawn from the 2MASS Large Galaxy Atlas (LGA). We supplement the LGA sample with dwarf galaxies and more distant giant ellipticals. Low surface brightness halos exceeding 50 kpc in diameter are found only in galaxies more luminous than L*, and classic interaction signatures are relatively infrequent. Halo diameter is correlated with total galaxy luminosity. Extended low surface brightness halos are present even in galaxies as faint as MV = - 18. Edge-on galaxies with boxy bulges tend to lack extended spheroidal halos, while those with large classical bulges exhibit extended round halos, supporting the notions that boxy or barlike bulges originate from disks. Most face-on spiral galaxies present features that appear to be irregular extensions of spiral arms, although rare cases show smooth boundaries with no sign of star formation. Although we serendipitously discovered a dwarf galaxy undergoing tidal disruption in the halo of NGC 4449, we found no comparable examples in our general survey. A search for similar examples in the Local Volume identified hcc087, a tidally disrupting dwarf galaxy in the Hercules Cluster, but we do not confirm an anomalously large half-light radius reported for the dwarf VCC 1661.

  16. The Stellar Density Profile of the Distant Galactic Halo

    NASA Astrophysics Data System (ADS)

    Slater, Colin T.; Nidever, David L.; Munn, Jeffrey A.; Bell, Eric F.; Majewski, Steven R.

    2016-12-01

    We use extensive gravity-sensitive DDO 51 photometry over 5100 square degrees, combined with Sloan Digital Sky Survey broadband photometry, to select a catalog of ˜4000 giant stars covering a large fraction of the high Galactic latitude sky and reaching out to ˜80 kpc in the Galactic halo. This sample of bright and unbiased tracers enables us to measure the radial profile and 3D structure of the stellar halo to large distances, which had previously only been measured with sparse tracers or small samples. Using population synthesis models to reproduce the observed giant star luminosity function, we find that the halo maintains a {r}-3.5 profile from 30 to 80 kpc with no signs of a truncation or sharp break over this range. The radial profile measurement is largely insensitive to individual halo substructure components, but we find that attempting to measure the shape of the halo is overwhelmed by the Sagittarius stream such that no elliposidal shape is a satisfactory description in this region. These measurements allow us to begin placing the Milky Way in context with the growing sample of external galaxies where similar halo profile measurements are available, with the goal of further linking the properties of stellar halos to the accretion histories that formed them.

  17. Renormalized halo bias

    SciTech Connect

    Assassi, Valentin; Baumann, Daniel; Green, Daniel; Zaldarriaga, Matias E-mail: dbaumann@damtp.cam.ac.uk E-mail: matiasz@ias.edu

    2014-08-01

    This paper provides a systematic study of renormalization in models of halo biasing. Building on work of McDonald, we show that Eulerian biasing is only consistent with renormalization if non-local terms and higher-derivative contributions are included in the biasing model. We explicitly determine the complete list of required bias parameters for Gaussian initial conditions, up to quartic order in the dark matter density contrast and at leading order in derivatives. At quadratic order, this means including the gravitational tidal tensor, while at cubic order the velocity potential appears as an independent degree of freedom. Our study naturally leads to an effective theory of biasing in which the halo density is written as a double expansion in fluctuations and spatial derivatives. We show that the bias expansion can be organized in terms of Galileon operators which aren't renormalized at leading order in derivatives. Finally, we discuss how the renormalized bias parameters impact the statistics of halos.

  18. Halo Nonlinear Reconstruction

    NASA Astrophysics Data System (ADS)

    Yu, Yu; Zhu, Hong-Ming; Pen, Ue-Li

    2017-10-01

    We apply the nonlinear reconstruction method to simulated halo fields. For halo number density 2.77 × {10}-2 {({h}-1{Mpc})}-3 at z = 0, corresponding to the SDSS main sample density, we find that the scale where the noise saturates the linear signal is improved to k≳ 0.36 h {{Mpc}}-1, which is a factor of 2.29 improvement in scale, or 12 in number of linear modes. The improvement is less for higher redshift or lower halo density. We expect this to substantially improve the BAO accuracy of dense, low-redshift surveys, including the SDSS main sample, 6dFGS and 21 cm intensity mapping initiatives.

  19. Origins of Stellar Halos

    NASA Astrophysics Data System (ADS)

    Johnston, Kathryn V.

    2016-08-01

    This contribution reviews ideas about the origins of stellar halos. It includes discussion of the theoretical understanding of and observational evidence for stellar populations formed ``in situ'' (meaning formed in orbits close to their current ones), ``kicked-out'' (meaning formed in the inner galaxy in orbits unlike their current ones) and ``accreted'' (meaning formed in a dark matter halo other than the one they currently occupy). At this point there is general agreement that a significant fraction of any stellar halo population is likely ``accreted''. There is modest evidence for the presence of a ``kicked-out'' population around both the Milky Way and M31. Our theoretical understanding of and the observational evidence for an ``in situ'' population are less clear.

  20. Magnetic spiral arms in galaxy haloes

    NASA Astrophysics Data System (ADS)

    Henriksen, R. N.

    2017-08-01

    We seek the conditions for a steady mean field galactic dynamo. The parameter set is reduced to those appearing in the α2 and α/ω dynamo, namely velocity amplitudes, and the ratio of sub-scale helicity to diffusivity. The parameters can be allowed to vary on conical spirals. We analyse the mean field dynamo equations in terms of scale invariant logarithmic spiral modes and special exact solutions. Compatible scale invariant gravitational spiral arms are introduced and illustrated in an appendix, but the detailed dynamical interaction with the magnetic field is left for another work. As a result of planar magnetic spirals `lifting' into the halo, multiple sign changes in average rotation measures forming a regular pattern on each side of the galactic minor axis, are predicted. Such changes have recently been detected in the Continuum Halos in Nearby Galaxies-an EVLA Survey (CHANG-ES) survey.

  1. Signes Iconiques, Signes Linguistiques (Iconic Signs, Linguistic Signs)

    ERIC Educational Resources Information Center

    Besse, Henri

    1974-01-01

    This article discusses the audiovisual image as sign; the classification of signs according to two different semiologies, and two different semantic theories; and the relation to different pedagogical approaches. (Text is in French.) (AM)

  2. The Outer Halo -- Halo Origins and Mass of the Galaxy

    NASA Astrophysics Data System (ADS)

    Morrison, Heather; Arabadjis, John; Dohm-Palmer, Robbie; Freeman, Ken; Harding, Paul; Mateo, Mario; Norris, John; Olszewski, Ed; Sneden, Chris

    2000-02-01

    Through our detection of distant halo stars, we are now well placed to map the regions of the Galactic halo where previously only satellite galaxies and a few globular clusters were known. Mapping this region is crucial for answering questions like: How and over what timescales was the Milky Way's stellar halo assembled? What is the total mass and shape of its dark halo? The Sagittarius dwarf has demonstrated that at least some of the stellar halo was accreted. But, HOW MUCH of the halo was accreted? Our previous efforts have proven that the Washington photometric system, in conjuction with spectroscopy, is capable of efficiently and unambiguously identifying halo stars out to 100 kpc or more. We require followup spectroscopy to map velocity substructure, which is more likely visible in the outer halo because of the long dynamical timescales, and to identify the rare objects in the extreme outer halo which will constrain the shape and size of its dark halo. We are applying for 4m/RCSP time at both CTIO and KPNO to observe faint outer-halo giant and BHB candidates.

  3. What's a Halo?

    MedlinePlus

    ... to school, doing schoolwork, and participating in extracurricular clubs, as long as they're feeling up to it and the doctor says it's OK. Your child's doctor will tell you what activities your child should avoid while in a halo brace. Sports will have to be put on hold for ...

  4. Stability of halo orbits.

    PubMed

    Howard, J E; Dullin, H R; Horányi, M

    2000-04-10

    We predict new populations of trapped nonequatorial ("halo") orbits of charged dust grains about an arbitrary axisymmetric planet. Simple equilibrium and stability conditions are derived, revealing dramatic differences between positively and negatively charged grains in prograde or retrograde orbits. Implications for the Cassini mission to Saturn are discussed.

  5. Halos in Martian Sandstone

    NASA Image and Video Library

    2017-05-30

    Pale zones called "halos" border bedrock fractures visible in this 2015 image from NASA's Curiosity Mars rover which has been darkened (a previously released image can be seen at PIA20268). Measurements overlaid on the image offer a sense of scale for the size of these fractures. The rover team determined that the halos are rich in silica, a clue to the duration of wet environmental conditions long ago. The location is on the lower slope of Mars' Mount Sharp. Curiosity's Navigation Camera (Navcam) acquired the component images of this mosaic on Aug. 23, 2015, during the 1.083rd Martian day, or sol, of the mission. The location is along the rover's path between "Marias Pass" and "Bridger Basin." In this region, the rover has found fracture zones to be associated with rock compositions enriched in silica, relative to surrounding bedrock. https://photojournal.jpl.nasa.gov/catalog/PIA21649

  6. GALACTIC WARPS IN TRIAXIAL HALOS

    SciTech Connect

    Jeon, Myoungwon; Kim, Sungsoo S.; Ann, Hong Bae E-mail: sungsoo.kim@khu.ac.kr

    2009-05-10

    We study the behavior of galactic disks in triaxial halos both numerically and analytically to see if warps can be excited and sustained in triaxial potentials. We consider the following two scenarios: (1) galactic disks that are initially tilted relative to the equatorial plane of the halo (for a pedagogical purpose), and (2) tilted infall of dark matter relative to the equatorial plane of the disk and the halo. With numerical simulations of 100,000 disk particles in a fixed halo potential, we find that in triaxial halos, warps can be excited and sustained just as in spherical or axisymmetric halos but they show some oscillatory behavior and even can be transformed to a polar-ring system if the halo has a prolate-like triaxiality. The nonaxisymmetric component of the halo causes the disk to nutate, and the differential nutation between the inner and outer parts of the disk generally makes the magnitude of the warp slightly diminish and fluctuate. We also find that warps are relatively weaker in oblate and oblate-like triaxial halos, and since these halos are the halo configurations of disk galaxies inferred by cosmological simulations, our results are consistent with the fact that most of the observed warps are quite weak. We derive approximate formulae for the torques exerted on the disk by the triaxial halo and the dark matter torus, and with these formulae we successfully describe the behavior of the disks in our simulations. The techniques used in deriving these formulae could be applied for realistic halos with more complex structures.

  7. Search for Halo Axions

    SciTech Connect

    Daw, E. J.,; van Bibber, K.

    1998-01-01

    A collaboration of MIT, LLNL, Univ. of Florida, FNAL, UC Berkeley and INR Moscow have built a large-scale RF cavity axion detector. The experiment has been taking production data since February of 1996 and is sensitive enough to detect plausible dark matter axions comprising a reasonable fraction of the mass in our galactic halo. After a brief introduction to axion physics, I discuss details of our instrumentation, our analysis methodology, our run plan and future goals of the experiments.

  8. Rainbows, halos, and glories.

    NASA Astrophysics Data System (ADS)

    Greenler, R.

    Paperback edition of the book first published in 1980 (31.003.052). Contents: 1. Rainbows. 2. Ice-crystal refraction effects: halos, arcs, and spots. 3. Ice-crystal reflection effects: pillars, circles, and crosses. 4. Complex displays, past and present. 5. Scattering: light in the sky and color in the clouds. 6. Diffraction: the corona, the glory, and the specter of the Brocken. 7. Atmospheric refraction: mirages, twinkling stars, and the green flash.

  9. Halo Star Lithium Depletion

    SciTech Connect

    Pinsonneault, M. H.; Walker, T. P.; Steigman, G.; Narayanan, Vijay K.

    1999-12-10

    The depletion of lithium during the pre-main-sequence and main-sequence phases of stellar evolution plays a crucial role in the comparison of the predictions of big bang nucleosynthesis with the abundances observed in halo stars. Previous work has indicated a wide range of possible depletion factors, ranging from minimal in standard (nonrotating) stellar models to as much as an order of magnitude in models that include rotational mixing. Recent progress in the study of the angular momentum evolution of low-mass stars permits the construction of theoretical models capable of reproducing the angular momentum evolution of low-mass open cluster stars. The distribution of initial angular momenta can be inferred from stellar rotation data in young open clusters. In this paper we report on the application of these models to the study of lithium depletion in main-sequence halo stars. A range of initial angular momenta produces a range of lithium depletion factors on the main sequence. Using the distribution of initial conditions inferred from young open clusters leads to a well-defined halo lithium plateau with modest scatter and a small population of outliers. The mass-dependent angular momentum loss law inferred from open cluster studies produces a nearly flat plateau, unlike previous models that exhibited a downward curvature for hotter temperatures in the 7Li-Teff plane. The overall depletion factor for the plateau stars is sensitive primarily to the solar initial angular momentum used in the calibration for the mixing diffusion coefficients. Uncertainties remain in the treatment of the internal angular momentum transport in the models, and the potential impact of these uncertainties on our results is discussed. The 6Li/7Li depletion ratio is also examined. We find that the dispersion in the plateau and the 6Li/7Li depletion ratio scale with the absolute 7Li depletion in the plateau, and we use observational data to set bounds on the 7Li depletion in main-sequence halo

  10. Halo-free phase contrast microscopy (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Nguyen, Tan H.; Kandel, Mikhail E.; Shakir, Haadi M.; Best, Catherine; Do, Minh N.; Popescu, Gabriel

    2017-02-01

    The phase contrast (PC) method is one of the most impactful developments in the four-century long history of microscopy. It allows for intrinsic, nondestructive contrast of transparent specimens, such as live cells. However, PC is plagued by the halo artifact, a result of insufficient spatial coherence in the illumination field, which limits its applicability. We present a new approach for retrieving halo-free phase contrast microscopy (hfPC) images by upgrading the conventional PC microscope with an external interferometric module, which generates sufficient data for reversing the halo artifact. Measuring four independent intensity images, our approach first measures haloed phase maps of the sample. We solve for the halo-free sample transmission function by using a physical model of the image formation under partial spatial coherence. Using this halo-free sample transmission, we can numerically generate artifact-free PC images. Furthermore, this transmission can be further used to obtain quantitative information about the sample, e.g., the thickness with known refractive indices, dry mass of live cells during their cycles. We tested our hfPC method on various control samples, e.g., beads, pillars and validated its potential for biological investigation by imaging live HeLa cells, red blood cells, and neurons.

  11. "Halo nevi" and UV radiation.

    PubMed

    Pustisek, Nives; Sikanić-Dugić, Nives; Hirsl-Hećej, Vlasta; Domljan, Mislav Luka

    2010-04-01

    Halo nevi, also termed Sutton nevi, are defined as benign melanocytic nevi that are surrounded by an area of depigmentation resembling a halo. Halo nevi are common in children and young adults, with a mean age at onset of 15 years. The incidence in the population is estimated to be approximately 1%. Affected individuals frequently have multiple lesions which are usually localized on the back. A familial tendency for halo nevi has been reported. The etiology of halo nevi is unknown. It is an autoimmune response and T lymphocytes are considered to play a key role in the progressive destruction of nevus cells. Halo nevi may be associated with autoimmune disorders such as vitiligo, Hashimoto thyroiditis, alopecia areata, celiac disease, atopic dermatitis and others. It has been proved that halo nevi are detected after an intense sun exposure especially after sunburns. The etiology of halo nevi, association with malignant melanoma and the role of sun exposure in the development of halo nevi are discussed.

  12. Microscopic interpretation of sign reversal in the electrocaloric effect in a ferroelectric PbMg1/3Nb2/3O3-30PbTiO3 single crystal

    NASA Astrophysics Data System (ADS)

    Axelsson, A.-K.; Le Goupil, F.; Dunne, L. J.; Manos, G.; Valant, M.; Alford, N. McN.

    2013-03-01

    With increasing temperature, PbMg1/3Nb2/3O3-30PbTiO3 (PMN-30PT) crystals change from pseudo-rhombohedral to tetragonal to cubic phases. In addition to the usual positive electrocaloric effect (ECE), a negative ECE, whose origin is uncertain, is observed. Here, these two types of the ECE contributions in PbMg1/3Nb2/3O3-30PbTiO3 crystals are modelled theoretically using a one dimensional statistical mechanical lattice model, which is solved by an exact matrix method. The quasi one-dimensional model reproduces the trends in the experimental behaviour and attributes the electrocaloric sign reversal to free energy changes induced by the electric field.

  13. Jupiter's Ring Halo

    NASA Technical Reports Server (NTRS)

    1997-01-01

    A mosaic of four images taken through the clear filter (610 nanometers) of the solid state imaging (CCD) system aboard NASA's Galileo spacecraft on November 8, 1996, at a resolution of approximately 46 kilometers (km) per picture element (pixel) along the rings; however, because the spacecraft was only about 0.5 degrees above the ring plane, the image is highly foreshortened in the vertical direction. The images were obtained when Galileo was in Jupiter's shadow peering back toward the Sun; the ring was approximately 2,300,000 kilometers (km) away. The arc on the far right of the image is produced by sunlight scattered by small particles comprising Jupiter's upper atmospheric haze. The ring also efficiently scatters light, indicating that much of its brightness is due to particles that are microns or less in diameter. Such small particles are believed to have human-scale lifetimes, i.e., very brief compared to the solar system's age.

    Jupiter's ring system is composed of three parts -- a flat main ring, a lenticular halo interior to the main ring, and the gossamer ring, which lies exterior to the main ring. The near and far arms of Jupiter's main ring extend horizontally across the mosaic, joining together at the ring's ansa, on the far left side of the figure. The near arm of the ring appears to be abruptly truncated close to the planet, at the point where it passes into Jupiter's shadow.

    A faint mist of particles can be seen above and below the main rings; this vertically extended, toroidal 'halo' is unusual in planetary rings, and is probably caused by electromagnetic forces which can push small grains out of the ring plane. Halo material is present across this entire image, implying that it reaches more than 27,000 km above the ring plane. Because of shadowing, the halo is not visible close to Jupiter in the lower right part of the mosaic. In order to accentuate faint features in the image, different brightnesses are shown through color, with the brightest

  14. Jupiter's Ring Halo

    NASA Technical Reports Server (NTRS)

    1997-01-01

    A mosaic of four images taken through the clear filter (610 nanometers) of the solid state imaging (CCD) system aboard NASA's Galileo spacecraft on November 8, 1996, at a resolution of approximately 46 kilometers (km) per picture element (pixel) along the rings; however, because the spacecraft was only about 0.5 degrees above the ring plane, the image is highly foreshortened in the vertical direction. The images were obtained when Galileo was in Jupiter's shadow peering back toward the Sun; the ring was approximately 2,300,000 kilometers (km) away. The arc on the far right of the image is produced by sunlight scattered by small particles comprising Jupiter's upper atmospheric haze. The ring also efficiently scatters light, indicating that much of its brightness is due to particles that are microns or less in diameter. Such small particles are believed to have human-scale lifetimes, i.e., very brief compared to the solar system's age.

    Jupiter's ring system is composed of three parts -- a flat main ring, a lenticular halo interior to the main ring, and the gossamer ring, which lies exterior to the main ring. The near and far arms of Jupiter's main ring extend horizontally across the mosaic, joining together at the ring's ansa, on the far left side of the figure. The near arm of the ring appears to be abruptly truncated close to the planet, at the point where it passes into Jupiter's shadow.

    A faint mist of particles can be seen above and below the main rings; this vertically extended, toroidal 'halo' is unusual in planetary rings, and is probably caused by electromagnetic forces which can push small grains out of the ring plane. Halo material is present across this entire image, implying that it reaches more than 27,000 km above the ring plane. Because of shadowing, the halo is not visible close to Jupiter in the lower right part of the mosaic. In order to accentuate faint features in the image, different brightnesses are shown through color, with the brightest

  15. Jupiter Ring Halo

    NASA Image and Video Library

    1998-03-26

    A mosaic of four images taken through the clear filter (610 nanometers) of the solid state imaging (CCD) system aboard NASA's Galileo spacecraft on November 8, 1996, at a resolution of approximately 46 kilometers (km) per picture element (pixel) along the rings; however, because the spacecraft was only about 0.5 degrees above the ring plane, the image is highly foreshortened in the vertical direction. The images were obtained when Galileo was in Jupiter's shadow peering back toward the Sun; the ring was approximately 2,300,000 kilometers (km) away. The arc on the far right of the image is produced by sunlight scattered by small particles comprising Jupiter's upper atmospheric haze. The ring also efficiently scatters light, indicating that much of its brightness is due to particles that are microns or less in diameter. Such small particles are believed to have human-scale lifetimes, i.e., very brief compared to the solar system's age. Jupiter's ring system is composed of three parts -- a flat main ring, a lenticular halo interior to the main ring, and the gossamer ring, which lies exterior to the main ring. The near and far arms of Jupiter's main ring extend horizontally across the mosaic, joining together at the ring's ansa, on the far left side of the figure. The near arm of the ring appears to be abruptly truncated close to the planet, at the point where it passes into Jupiter's shadow. A faint mist of particles can be seen above and below the main rings; this vertically extended, toroidal "halo" is unusual in planetary rings, and is probably caused by electromagnetic forces which can push small grains out of the ring plane. Halo material is present across this entire image, implying that it reaches more than 27,000 km above the ring plane. Because of shadowing, the halo is not visible close to Jupiter in the lower right part of the mosaic. In order to accentuate faint features in the image, different brightnesses are shown through color, with the brightest being

  16. Vital Signs

    MedlinePlus

    ... and your weight. Respiratory rate, which measures your breathing. Mild breathing changes can be from causes such as a ... nose or hard exercise. But slow or fast breathing can also be a sign of a serious ...

  17. Reversal of the sign of the temperature dependence of the dominant spin-spin correlation in the magnetic percolation Ising system Fe_0.25Zn_0.75F_2

    NASA Astrophysics Data System (ADS)

    Barber, W. C.; Slanic, Z.; Belanger, D. P.

    1998-03-01

    It has been shown experimentally and theoretically(J. Ferre and G.A. Gehring, Rep. Prog. Phys. 47, 513 (1984).) that d(Δ n)/dT is proportional to a sum of the temperature derivatives of the spin-spin correlations, d(_k)/dT, where k denotes different sets of neighbors. Near T_c, where all the correlations have the same T dependence, d(Δ n)/dT is proportional to the magnetic specific heat, C_m, in the dilute magnetic Ising system Fe_xZn_1-xF2 for x>0.3. We investigate d(Δ n)/dT for a single crystal of Fe_0.25Zn_0.75F_2, which is close to the magnetic percolation threshold. It is observed that d(Δ n)/dT surprisingly changes sign as the temperature is lowered below T=10 K. We also present Monte Carlo simulations which imply that frustration in the third-nearest neighbor exchange in this system can lead to a similar reversal in the sign of the temperature derivative of the dominant nearest-neighbor spin-spin correlation, consistent with the experimental results.

  18. HALOE test and evaluation software

    NASA Technical Reports Server (NTRS)

    Edmonds, W.; Natarajan, S.

    1987-01-01

    Computer programming, system development and analysis efforts during this contract were carried out in support of the Halogen Occultation Experiment (HALOE) at NASA/Langley. Support in the major areas of data acquisition and monitoring, data reduction and system development are described along with a brief explanation of the HALOE project. Documented listings of major software are located in the appendix.

  19. Vital signs: trends in use of long-acting reversible contraception among teens aged 15-19 years seeking contraceptive services—United States, 2005-2013.

    PubMed

    Romero, Lisa; Pazol, Karen; Warner, Lee; Gavin, Lorrie; Moskosky, Susan; Besera, Ghenet; Loyola Briceno, Ana Carolina; Jatlaoui, Tara; Barfield, Wanda

    2015-04-10

    Nationally, the use of long-acting reversible contraception (LARC), specifically intrauterine devices (IUDs) and implants, by teens remains low, despite their effectiveness, safety, and ease of use. To examine patterns in use of LARC among females aged 15-19 years seeking contraceptive services, CDC and the U.S. Department of Health and Human Services' Office of Population Affairs analyzed 2005-2013 data from the Title X National Family Planning Program. Title X serves approximately 1 million teens each year and provides family planning and related preventive health services for low-income persons. Use of LARC among teens seeking contraceptive services at Title X service sites increased from 0.4% in 2005 to 7.1% in 2013 (p-value for trend <0.001). Of the 616,148 female teens seeking contraceptive services in 2013, 17,349 (2.8%) used IUDs, and 26,347 (4.3%) used implants. Use of LARC was higher among teens aged 18-19 years (7.6%) versus 15-17 years (6.5%) (p<0.001). The percentage of teens aged 15-19 years who used LARC varied widely by state, from 0.7% (Mississippi) to 25.8% (Colorado). Although use of LARC by teens remains low nationwide, efforts to improve access to LARC among teens seeking contraception at Title X service sites have increased use of these methods. Health centers that provide quality contraceptive services can facilitate use of LARC among teens seeking contraception. Strategies to address provider barriers to offering LARC include: 1) educating providers that LARC is safe for teens; 2) training providers on LARC insertion and a client-centered counseling approach that includes discussing the most effective contraceptive methods first; and 3) providing contraception at reduced or no cost to the client.

  20. Neutron halo in deformed nuclei

    SciTech Connect

    Zhou Shangui; Meng Jie; Ring, P.; Zhao Enguang

    2010-07-15

    Halo phenomena in deformed nuclei are investigated within a deformed relativistic Hartree Bogoliubov (DRHB) theory. These weakly bound quantum systems present interesting examples for the study of the interdependence between the deformation of the core and the particles in the halo. Contributions of the halo, deformation effects, and large spatial extensions of these systems are described in a fully self-consistent way by the DRHB equations in a spherical Woods-Saxon basis with the proper asymptotic behavior at a large distance from the nuclear center. Magnesium and neon isotopes are studied and detailed results are presented for the deformed neutron-rich and weakly bound nucleus {sup 44}Mg. The core of this nucleus is prolate, but the halo has a slightly oblate shape. This indicates a decoupling of the halo orbitals from the deformation of the core. The generic conditions for the occurrence of this decoupling effects are discussed.

  1. Haloes gone MAD: The Halo-Finder Comparison Project

    NASA Astrophysics Data System (ADS)

    Knebe, Alexander; Knollmann, Steffen R.; Muldrew, Stuart I.; Pearce, Frazer R.; Aragon-Calvo, Miguel Angel; Ascasibar, Yago; Behroozi, Peter S.; Ceverino, Daniel; Colombi, Stephane; Diemand, Juerg; Dolag, Klaus; Falck, Bridget L.; Fasel, Patricia; Gardner, Jeff; Gottlöber, Stefan; Hsu, Chung-Hsing; Iannuzzi, Francesca; Klypin, Anatoly; Lukić, Zarija; Maciejewski, Michal; McBride, Cameron; Neyrinck, Mark C.; Planelles, Susana; Potter, Doug; Quilis, Vicent; Rasera, Yann; Read, Justin I.; Ricker, Paul M.; Roy, Fabrice; Springel, Volker; Stadel, Joachim; Stinson, Greg; Sutter, P. M.; Turchaninov, Victor; Tweed, Dylan; Yepes, Gustavo; Zemp, Marcel

    2011-08-01

    We present a detailed comparison of fundamental dark matter halo properties retrieved by a substantial number of different halo finders. These codes span a wide range of techniques including friends-of-friends, spherical-overdensity and phase-space-based algorithms. We further introduce a robust (and publicly available) suite of test scenarios that allow halo finder developers to compare the performance of their codes against those presented here. This set includes mock haloes containing various levels and distributions of substructure at a range of resolutions as well as a cosmological simulation of the large-scale structure of the universe. All the halo-finding codes tested could successfully recover the spatial location of our mock haloes. They further returned lists of particles (potentially) belonging to the object that led to coinciding values for the maximum of the circular velocity profile and the radius where it is reached. All the finders based in configuration space struggled to recover substructure that was located close to the centre of the host halo, and the radial dependence of the mass recovered varies from finder to finder. Those finders based in phase space could resolve central substructure although they found difficulties in accurately recovering its properties. Through a resolution study we found that most of the finders could not reliably recover substructure containing fewer than 30-40 particles. However, also here the phase-space finders excelled by resolving substructure down to 10-20 particles. By comparing the halo finders using a high-resolution cosmological volume, we found that they agree remarkably well on fundamental properties of astrophysical significance (e.g. mass, position, velocity and peak of the rotation curve). We further suggest to utilize the peak of the rotation curve, vmax, as a proxy for mass, given the arbitrariness in defining a proper halo edge. Airport code for Madrid, Spain

  2. Strong bimodality in the host halo mass of central galaxies from galaxy-galaxy lensing

    NASA Astrophysics Data System (ADS)

    Mandelbaum, Rachel; Wang, Wenting; Zu, Ying; White, Simon; Henriques, Bruno; More, Surhud

    2016-04-01

    We use galaxy-galaxy lensing to study the dark matter haloes surrounding a sample of locally brightest galaxies (LBGs) selected from the Sloan Digital Sky Survey. We measure mean halo mass as a function of the stellar mass and colour of the central galaxy. Mock catalogues constructed from semi-analytic galaxy formation simulations demonstrate that most LBGs are the central objects of their haloes, greatly reducing interpretation uncertainties due to satellite contributions to the lensing signal. Over the full stellar mass range, 10.3 < log [M*/M⊙] < 11.6, we find that passive central galaxies have haloes that are at least twice as massive as those of star-forming objects of the same stellar mass. The significance of this effect exceeds 3σ for log [M*/M⊙] > 10.7. Tests using the mock catalogues and on the data themselves clarify the effects of LBG selection and show that it cannot artificially induce a systematic dependence of halo mass on LBG colour. The bimodality in halo mass at fixed stellar mass is reproduced by the astrophysical model underlying our mock catalogue, but the sign of the effect is inconsistent with recent, nearly parameter-free age-matching models. The sign and magnitude of the effect can, however, be reproduced by halo occupation distribution models with a simple (few-parameter) prescription for type dependence.

  3. Vital Signs.

    ERIC Educational Resources Information Center

    Brown, Lester R.

    1993-01-01

    Presents an excerpt from the first edition of Vital Signs, a Worldwide Institute publication that provides an annual update on global environmental trends. Includes discussion of the dismantling of nuclear arms, reduction in chlorofluorocarbon production, growth in bicycle production, the decline in cigarette smoking, and decline in military…

  4. Vital signs

    MedlinePlus

    ... overall health. Normal vital sign ranges for the average healthy adult while resting are: Blood pressure: 90/60 mm/Hg to 120/80 mm/Hg Breathing: 12 to 18 breaths per minute Pulse: 60 to 100 beats per minute Temperature: 97.8°F to 99.1°F (36. ...

  5. Vital Signs.

    ERIC Educational Resources Information Center

    Brown, Lester R.

    1993-01-01

    Presents an excerpt from the first edition of Vital Signs, a Worldwide Institute publication that provides an annual update on global environmental trends. Includes discussion of the dismantling of nuclear arms, reduction in chlorofluorocarbon production, growth in bicycle production, the decline in cigarette smoking, and decline in military…

  6. Halo Shape and its Relation to Environment

    NASA Astrophysics Data System (ADS)

    Gottlöber, S.; Turchaninov, V.

    Using high resolution DM simulations we study the shape of dark matter halos. Halos become more spherical with decreasing mass. This trend is even more pronounced for the inner part of the halo. Angular momentum and shape are correlated. The angular momenta of neighboring halos are correlated.

  7. The surface density of haloes

    NASA Astrophysics Data System (ADS)

    Del Popolo, A.; Lee, Xi-Guo

    We study the correlation between the central surface density and the core radius of the dark matter haloes of galaxies and clusters of galaxies. We find that the surface density within the halo characteristic radius r* is not a universal quantity as claimed by some authors (e.g., Milgrom 2009), but it correlates with several physical quantities (e.g., the halo mass M200, and the magnitude MB). The slope of the surface density-mass relation is 0.18 ± 0.05, leaving small room to the possibility of a constant surface density. Finally, we compare the results with MOND predictions.

  8. Development of a reverse transcriptase-polymerase chain reaction assay to detect feline herpesvirus-1 latency-associated transcripts in the trigeminal ganglia and corneas of cats that did not have clinical signs of ocular disease.

    PubMed

    Townsend, Wendy M; Stiles, Jean; Guptill-Yoran, Lynn; Krohne, Sheryl G

    2004-03-01

    To develop a reverse transcriptase-polymerase chain reaction (RT-PCR) assay to detect feline herpesvirus-1 (FHV-1) latency-associated transcripts (LATs) in the corneas and trigeminal ganglia of cats that did not have clinical signs of ocular disease. Corneas and trigeminal ganglia obtained from 21 cats necropsied at the Indiana Animal Disease Diagnostic Laboratory and 25 cats euthanatized at a humane shelter; none of the cats had a recent history of respiratory tract or ocular disease, and all had normal results for ophthalmic examinations. Both corneas and both trigeminal ganglia were harvested from each cat. An initial PCR assay detected FHV-1 DNA in the corneas and trigeminal ganglia. The RNA was then isolated from samples positive for FHV-1 DNA, and an RT-PCR assay was used to detect LATs. FHV-1 DNA was detected in 45 of 92 (48.9%) corneas and 38 of 92 (41.3%) trigeminal ganglia. In many samples, the RNA had degraded and RT-PCR assay was not possible. Of the samples subjected to RT-PCR assay, none of the 39 corneas but 4 of 16 trigeminal ganglia had positive results when tested for LATs. Analysis of the results indicated that a high percentage of cats that did not have clinical signs of ocular disease had detectable FHV-1 DNA in their corneas and trigeminal ganglia. This study documents that the RT-PCR assay can successfully identify LATs and may serve as a tool to better understand the biologic characteristics of FHV-1 and its relationship to clinical disease.

  9. Halo model and halo properties in Galileon gravity cosmologies

    SciTech Connect

    Barreira, Alexandre; Li, Baojiu; Hellwing, Wojciech A.; Baugh, Carlton M.; Lombriser, Lucas; Pascoli, Silvia E-mail: baojiu.li@durham.ac.uk E-mail: llo@roe.ac.uk E-mail: silvia.pascoli@durham.ac.uk

    2014-04-01

    We investigate the performance of semi-analytical modelling of large-scale structure in Galileon gravity cosmologies using results from N-body simulations. We focus on the Cubic and Quartic Galileon models that provide a reasonable fit to CMB, SNIa and BAO data. We demonstrate that the Sheth-Tormen mass function and linear halo bias can be calibrated to provide a very good fit to our simulation results. We also find that the halo concentration-mass relation is well fitted by a power law. The nonlinear matter power spectrum computed in the halo model approach is found to be inaccurate in the mildly nonlinear regime, but captures reasonably well the effects of the Vainshtein screening mechanism on small scales. In the Cubic model, the screening mechanism hides essentially all of the effects of the fifth force inside haloes. In the case of the Quartic model, the screening mechanism leaves behind residual modifications to gravity, which make the effective gravitational strength time-varying and smaller than the standard value. Compared to normal gravity, this causes a deficiency of massive haloes and leads to a weaker matter clustering on small scales. For both models, we show that there are realistic halo occupation distributions of Luminous Red Galaxies that can match both the observed large-scale clustering amplitude and the number density of these galaxies.

  10. Sign reversal of the Hall effect in YBa{sub 2}(Cu{sub 1{minus}x}Co{sub x}){sub 3}O{sub 7{minus}{delta}} single crystals

    SciTech Connect

    Neiman, R.L.; Giapintzakis, J.; Ginsberg, D.M.

    1995-06-01

    The authors have measured the in-plane Hall effect and in-plane resistivity of cobalt-doped YBa{sub 2}Cu{sub 3}O{sub 7{minus}{delta}} (YBCO) single-crystal samples. The concentration of cobalt ranged from 1 to 3%. As the applied field was varied, a sign reversal of the Hall resistivity was seen for 1 and 2% Co-doped samples, but not for the 3% sample. These results are expressed in terms of conductivities, as recently recommended by the work of Dorsey et al. and Kopnin et al. In the mixed state just below the superconducting transition temperature T{sub c}, the Hall conductivity {sigma}{sub xy} is the sum of two terms, C{sub 1}/H and C{sub 2}H, where C{sub 1} and C{sub 2} are field-independent but temperature-dependent. As previously observed by Ginsberg and Manson for undoped YBCO, the coefficient C{sub 1} is approximately proportional to {tau}{sup 2} and C{sub 2} is approximately linear in {tau}, where {tau}=1{minus}(T/T{sub c}). The values of C{sub 1} and C{sub 2} are presented for each cobalt concentration.

  11. Coherence Effect of Sign-Reversing s±-Wave Cooper Pair State in Heavily Overdoped LaFeAsO-based Superconductor: 75As-Nuclear Quadrupole Resonance

    NASA Astrophysics Data System (ADS)

    Mukuda, Hidekazu; Nitta, Mariko; Yashima, Mitsuharu; Kitaoka, Yoshio; Shirage, Parasharam M.; Eisaki, Hiroshi; Iyo, Akira

    2010-11-01

    We report an 75As-nuclear quadrupole resonance (NQR) study on heavily electron-doped LaFeAsO1-xFx (La1111) with Tc=5 K. The measurement of the nuclear spin relaxation rate (1/T1) has revealed that a Hebel-Slichter (HS) peak partially recovers in heavily electron-overdoped regimes where the nesting condition of hole and electron Fermi surfaces (FSs) becomes significantly worse. This is in contrast to previous results reported for optimally doped La1111 with Tc=28 K that there is a lack of the HS peak. These results indicate that the interband scattering between the hole and electron FSs is strongly suppressed by an almost vanishing hole FS because of the heavy electron-overdoping. Our findings strongly suggest that the sign reversal of the gap functions on different FSs, that is, the s±-wave state, is realized in La1111 compounds. We remark that interband scattering on well-nested FSs is essential for stabilizing the s±-wave state and enhancing Tc up to 28 K in LaFeAsO-based superconductors.

  12. Halo modelling in chameleon theories

    SciTech Connect

    Lombriser, Lucas; Koyama, Kazuya; Li, Baojiu E-mail: kazuya.koyama@port.ac.uk

    2014-03-01

    We analyse modelling techniques for the large-scale structure formed in scalar-tensor theories of constant Brans-Dicke parameter which match the concordance model background expansion history and produce a chameleon suppression of the gravitational modification in high-density regions. Thereby, we use a mass and environment dependent chameleon spherical collapse model, the Sheth-Tormen halo mass function and linear halo bias, the Navarro-Frenk-White halo density profile, and the halo model. Furthermore, using the spherical collapse model, we extrapolate a chameleon mass-concentration scaling relation from a ΛCDM prescription calibrated to N-body simulations. We also provide constraints on the model parameters to ensure viability on local scales. We test our description of the halo mass function and nonlinear matter power spectrum against the respective observables extracted from large-volume and high-resolution N-body simulations in the limiting case of f(R) gravity, corresponding to a vanishing Brans-Dicke parameter. We find good agreement between the two; the halo model provides a good qualitative description of the shape of the relative enhancement of the f(R) matter power spectrum with respect to ΛCDM caused by the extra attractive gravitational force but fails to recover the correct amplitude. Introducing an effective linear power spectrum in the computation of the two-halo term to account for an underestimation of the chameleon suppression at intermediate scales in our approach, we accurately reproduce the measurements from the N-body simulations.

  13. Galactic Halos of Hydrogen

    NASA Technical Reports Server (NTRS)

    2005-01-01

    This image shows two companion galaxies, NGC 4625 (top) and NGC 4618 (bottom), and their surrounding cocoons of cool hydrogen gas (purple). The huge set of spiral arms on NGC 4625 (blue) was discovered by the ultraviolet eyes of NASA's Galaxy Evolution Explorer. Though these arms are nearly invisible when viewed in optical light, they glow brightly in ultraviolet. This is because they are bustling with hot, newborn stars that radiate primarily ultraviolet light.

    The vibrant spiral arms are also quite lengthy, stretching out to a distance four times the size of the galaxy's core. They are part of the largest ultraviolet galactic disk discovered so far.

    Astronomers do not know why NGC 4625 grew arms while NGC 4618 did not. The purple nebulosity shown here illustrates that hydrogen gas - an ingredient of star formation - is diffusely distributed around both galaxies. This means that other unknown factors led to the development of the arms of NGC 4625.

    Located 31 million light-years away in the constellation Canes Venatici, NGC 4625 is the closest galaxy ever seen with such a young halo of arms. It is slightly smaller than our Milky Way, both in size and mass. However, the fact that this galaxy's disk is forming stars very actively suggests that it might evolve into a more massive and mature galaxy resembling our own.

    The image is composed of ultraviolet, visible-light and radio data, from the Galaxy Evolution Explorer, the California Institute of Technology's Digitized Sky Survey, and the Westerbork Synthesis Radio Telescope, the Netherlands, respectively. Near-ultraviolet light is colored green; far-ultraviolet light is colored blue; and optical light is colored red. Radio emissions are colored purple.

  14. Building Halos by Digesting Satellites

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2016-05-01

    We think galactic halos are built through the addition of material from the smaller subhalos of satellites digested by their hosts. Though most of the stars in Milky-Way-mass halos were probably formed in situ, many were instead accumulated over time, as orbiting dwarf galaxies were torn apart and their stars flung throughout the host galaxy. A recent set of simulations has examined this brutal formation process.In the authors simulations, a subhalo first falls into the host halo. At this point, it can either survive to present day as a satellite galaxy, or it can be destroyed, its stars scattering throughout the host halo. [Deason et al. 2016]Subhalo FateThere are many open questions about the growth of Milky-Way-mass halos from the accretion of subhalos. Which subhalos are torn apart and accreted, and which ones survive intact? Are more small or large subhalos accreted? Does subhalo accretion affect the host galaxys metallicity? And what can we learn from all of this about the Milky Ways formation history?In a recently published study, a team of scientists from Stanford University and SLAC National Accelerator Laboratory set out to answer these questions using a suite of 45 zoom-in simulations of Milky-Way-mass halos. Led by Alis Deason, the team tracked the accretion history of these 45 test galaxies to determine how their halos were built.Piecing Together HistoryDeason and collaborators reach several new and interesting conclusions based on the outcomes of their simulations.Average accreted stellar mass from destroyed dwarfs for each host halo, as a function of the time of the last major accretion event. More stellar mass is accreted in more recent accretion events. [Deason et al. 2016]Most of the stellar mass accreted by the Milky-Way-mass halos typically comes from only one or two destroyed dwarfs. The accreted dwarfs are usually low-mass if they were accreted early on in the simulation (i.e., in the early universe), and high-mass if they were accreted

  15. Dynamics of an interacting luminous disc, dark halo and satellite companion

    NASA Astrophysics Data System (ADS)

    Weinberg, Martin D.

    1998-09-01

    This paper describes a method, based on linear perturbation theory, to determine the dynamical interaction between extended halo and spheroid components and an environmental disturbance. One finds that resonant interaction between a galaxy and passing interlopers or satellite companions can carry the disturbance inward, deep inside the halo, where it can perturb the disc. Applied to the Milky Way for example, the LMC and SMC appear to be sufficient to cause the observed Galactic warp and possibly seed other asymmetries. This is a multi-scale interaction in which the halo wake has a feature at roughly half the satellite orbital radius owing to a 2:1 orbital resonance. The rotating disturbance then excites an m=1 vertical disc mode which has the classic integral-sign morphology. A polar satellite orbit produces the largest warp and therefore the inferred LMC orbit is nearly optimal for maximum warp production. Both the magnitude and morphology of the response depend on the details of the disc and halo models. Most critically, a change in the halo profile will shift the resonant frequencies and response location and consequently alter the coupling to the bending disc. Increasing the halo support relative to the disc, a sub-maximal disc model, decreases the warp amplitude. Finally, the results and prognosis for N-body simulations are discussed. Discreteness noise in the halo, similar to that arising from a population of 10^6-Msolar black holes, can produce observable warping.

  16. Universality in Molecular Halo Clusters

    NASA Astrophysics Data System (ADS)

    Stipanović, P.; Markić, L. Vranješ; Bešlić, I.; Boronat, J.

    2014-12-01

    The ground state of weakly bound dimers and trimers with a radius extending well into the classically forbidden region is explored, with the goal to test the predicted universality of quantum halo states. The focus of the study is molecules consisting of T ↓ , D ↓ , 3He, 4He, and alkali atoms, where the interaction between particles is much better known than in the case of nuclei, which are traditional examples of quantum halos. The study of realistic systems is supplemented by model calculations in order to analyze how low-energy properties depend on the interaction potential. The use of variational and diffusion Monte Carlo methods enabled a very precise calculation of both the size and binding energy of the trimers. In the quantum halo regime, and for large values of scaled binding energies, all clusters follow almost the same universal line. As the scaled binding energy decreases, Borromean states separate from tango trimers.

  17. Accretion in the galactic halo

    NASA Astrophysics Data System (ADS)

    Stephens, Alex Courtney

    2000-10-01

    The Milky Way disk is enveloped in a diffuse, dynamically-hot collection of stars and star clusters collectively known as the ``stellar halo''. Photometric and chemical analyses suggest that these stars are ancient fossils of the galaxy formation epoch. Yet, little is known about the origin of this trace population. Is this system merely a vestige of the initial burst of star formation within the decoupled proto-Galaxy, or is it the detritus of cannibalized satellite galaxies? In an attempt to unravel the history of the Milky Way's stellar halo, I performed a detailed spectroscopic analysis of 55 metal-poor stars possessing ``extreme'' kinematic properties. It is thought that stars on orbits that either penetrate the remote halo or exhibit large retrograde velocities could have been associated with assimilated (or ``accreted'') dwarf galaxies. The hallmark of an accreted halo star is presumed to be a deficiency (compared with normal stars) of the α-elements (O, Mg, Si, Ca, Ti) with respect to iron, a consequence of sporadic bursts of star formation within the diminutive galaxies. Abundances for a select group of light metals (Li, Na, Mg, Si, Ca, Ti), iron-peak nuclides (Cr, Fe, Ni), and neutron-capture elements (Y, Ba) were calculated using line-strengths measured from high-resolution, high signal-to-noise spectral observations collected with the Keck I 10-m and KPNO 4-m telescopes. The abundances extracted from the spectra reveal: (1)The vast majority of outer halo stars possess supersolar [α/Fe] > 0.0) ratios. (2)The [α/Fe] ratio appears to decrease with increasing metallicity. (3)The outer halo stars have lower ratios of [α/Fe] than inner halo stars at a given metallicity. (4)At the largest metallicities, there is a large spread in the observed [α/Fe] ratios. (5)[α/Fe] anti-correlates with RAPO. (6)Only one star (BD+80° 245) exhibits the peculiar abundances expected of an assimilated star. The general conclusion extracted from these data is that the

  18. POPULATION III STAR FORMATION IN LARGE COSMOLOGICAL VOLUMES. I. HALO TEMPORAL AND PHYSICAL ENVIRONMENT

    SciTech Connect

    Crosby, Brian D.; O'Shea, Brian W.; Smith, Britton D.; Turk, Matthew J.; Hahn, Oliver

    2013-08-20

    We present a semi-analytic, computationally inexpensive model to identify halos capable of forming a Population III star in cosmological simulations across a wide range of times and environments. This allows for a much more complete and representative set of Population III star forming halos to be constructed, which will lead to Population III star formation simulations that more accurately reflect the diversity of Population III stars, both in time and halo mass. This model shows that Population III and chemically enriched stars coexist beyond the formation of the first generation of stars in a cosmological simulation until at least z {approx} 10, and likely beyond, though Population III stars form at rates that are 4-6 orders of magnitude lower than chemically enriched stars by z = 10. A catalog of more than 40,000 candidate Population III forming halos were identified, with formation times temporally ranging from z = 30 to z = 10, and ranging in mass from 2.3 Multiplication-Sign 10{sup 5} M{sub Sun} to 1.2 Multiplication-Sign 10{sup 10} M{sub Sun }. At early times, the environment that Population III stars form in is very similar to that of halos hosting chemically enriched star formation. At later times Population III stars are found to form in low-density regions that are not yet chemically polluted due to a lack of previous star formation in the area. Population III star forming halos become increasingly spatially isolated from one another at later times, and are generally closer to halos hosting chemically enriched star formation than to another halo hosting Population III star formation by z {approx} 10.

  19. White Dwarfs in the Galaxy's Halo

    NASA Astrophysics Data System (ADS)

    Oppenheimer, B.; Murdin, P.

    2002-12-01

    The Galaxy's large spherical halo (see GALACTICMETAL-POOR HALO and HALO, GALACTIC) may harboras many as several hundred billion WHITE DWARFS, apopulation as large in number as the total number of stars in theGalaxy's disk (see DISK GALAXIES and GALACTIC THIN DISK). Although this assertion iscontroversial, several astronomical surveys provide strong support for it andthe implications affect fields ...

  20. Dermoscopy of halo nevus in own observation

    PubMed Central

    Szymszal, Jan

    2014-01-01

    Introduction Halo nevus (HN) is a rare dermatologic entity characterized by a typical whitish rim encircling the existing melanocytic nevus resembling a halo. The clinical picture is suggesting its diagnosis, but so far only several dermoscopic descriptions of halo nevus have existed in the PubMed database. Aim To present the clinical and dermoscopic characteristics of halo nevus observed in dermoscopy. Material and methods Fifteen patients were diagnosed clinically and dermoscopically with halo nevus during planned routine dermoscopic examinations of all melanocytic lesions in 2007–2013. All digital images stored in the computer database were analyzed retrospectively according to the procedure described in the study. The clinical and dermoscopic parameters such as the dermoscopic pattern, color of nevus, special features and description of the surrounding halo were analyzed statistically. Results We analyzed 22 halo nevi (9 in females, 13 in males) in 15 patients (7 females, 8 males) diagnosed during the dermoscopic examination. The mean age of patients during dermoscopic examinations was 18.2 years. Mean patients’ age at HN onset was 15.7 years. Halo nevi occurred the most often as a solitary lesion. The ratio of multiple halo nevi to solitary halo nevus was 5 : 10. Every third halo nevus was located on the posterior trunk upper. In 68.2% of HN cases, the surrounding rim (halo) was characterized by its homogenous, whitish color. Conclusions Dermoscopic patterns such as uniform globular and structureless constituted one-third each of them in all analyzed patterns. PMID:25097486

  1. Dermoscopy of halo nevus in own observation.

    PubMed

    Kamińska-Winciorek, Grażyna; Szymszal, Jan

    2014-06-01

    Halo nevus (HN) is a rare dermatologic entity characterized by a typical whitish rim encircling the existing melanocytic nevus resembling a halo. The clinical picture is suggesting its diagnosis, but so far only several dermoscopic descriptions of halo nevus have existed in the PubMed database. To present the clinical and dermoscopic characteristics of halo nevus observed in dermoscopy. Fifteen patients were diagnosed clinically and dermoscopically with halo nevus during planned routine dermoscopic examinations of all melanocytic lesions in 2007-2013. All digital images stored in the computer database were analyzed retrospectively according to the procedure described in the study. The clinical and dermoscopic parameters such as the dermoscopic pattern, color of nevus, special features and description of the surrounding halo were analyzed statistically. We analyzed 22 halo nevi (9 in females, 13 in males) in 15 patients (7 females, 8 males) diagnosed during the dermoscopic examination. The mean age of patients during dermoscopic examinations was 18.2 years. Mean patients' age at HN onset was 15.7 years. Halo nevi occurred the most often as a solitary lesion. The ratio of multiple halo nevi to solitary halo nevus was 5 : 10. Every third halo nevus was located on the posterior trunk upper. In 68.2% of HN cases, the surrounding rim (halo) was characterized by its homogenous, whitish color. Dermoscopic patterns such as uniform globular and structureless constituted one-third each of them in all analyzed patterns.

  2. Non-Gaussian halo assembly bias

    SciTech Connect

    Reid, Beth A.; Verde, Licia; Dolag, Klaus; Matarrese, Sabino; Moscardini, Lauro E-mail: liciaverde@icc.ub.edu E-mail: sabino.matarrese@pd.infn.it

    2010-07-01

    The strong dependence of the large-scale dark matter halo bias on the (local) non-Gaussianity parameter, f{sub NL}, offers a promising avenue towards constraining primordial non-Gaussianity with large-scale structure surveys. In this paper, we present the first detection of the dependence of the non-Gaussian halo bias on halo formation history using N-body simulations. We also present an analytic derivation of the expected signal based on the extended Press-Schechter formalism. In excellent agreement with our analytic prediction, we find that the halo formation history-dependent contribution to the non-Gaussian halo bias (which we call non-Gaussian halo assembly bias) can be factorized in a form approximately independent of redshift and halo mass. The correction to the non-Gaussian halo bias due to the halo formation history can be as large as 100%, with a suppression of the signal for recently formed halos and enhancement for old halos. This could in principle be a problem for realistic galaxy surveys if observational selection effects were to pick galaxies occupying only recently formed halos. Current semi-analytic galaxy formation models, for example, imply an enhancement in the expected signal of ∼ 23% and ∼ 48% for galaxies at z = 1 selected by stellar mass and star formation rate, respectively.

  3. THE STELLAR HALOS OF MASSIVE ELLIPTICAL GALAXIES

    SciTech Connect

    Greene, Jenny E.; Murphy, Jeremy D.; Comerford, Julia M.; Gebhardt, Karl; Adams, Joshua J.

    2012-05-01

    We use the Mitchell Spectrograph (formerly VIRUS-P) on the McDonald Observatory 2.7 m Harlan J. Smith Telescope to search for the chemical signatures of massive elliptical galaxy assembly. The Mitchell Spectrograph is an integral-field spectrograph with a uniquely wide field of view (107'' Multiplication-Sign 107''), allowing us to achieve remarkably high signal-to-noise ratios of {approx}20-70 pixel{sup -1} in radial bins of 2-2.5 times the effective radii of the eight galaxies in our sample. Focusing on a sample of massive elliptical galaxies with stellar velocity dispersions {sigma}{sub *} > 150 km s{sup -1}, we study the radial dependence in the equivalent widths (EW) of key metal absorption lines. By twice the effective radius, the Mgb EWs have dropped by {approx}50%, and only a weak correlation between {sigma}{sub *} and Mgb EW remains. The Mgb EWs at large radii are comparable to those seen in the centers of elliptical galaxies that are {approx} an order of magnitude less massive. We find that the well-known metallicity gradients often observed within an effective radius continue smoothly to 2.5 R{sub e} , while the abundance ratio gradients remain flat. Much like the halo of the Milky Way, the stellar halos of our galaxies have low metallicities and high {alpha}-abundance ratios, as expected for very old stars formed in small stellar systems. Our observations support a picture in which the outer parts of massive elliptical galaxies are built by the accretion of much smaller systems whose star formation history was truncated at early times.

  4. Signing off

    NASA Astrophysics Data System (ADS)

    2001-05-01

    sharp that they cause paper cuts. Stains. If you accidentally spill some food or drink on your clothes, make sure you attempt to remove it as soon as possible and preferably within the same lunar cycle. Some teachers seem to think they should be worn with pride like the stains on a chemistry teacher's white coat. This is a myth. Materials. For scientists continually teaching about the wonder of smart materials, physics teachers are remarkably conservative in their choice of materials for their clothes. Try to break out from the traditional corduroy and tweed and practise what you teach. It is not acceptable to wear the actual tie you wore at school, as this will be at least 20 years old, be rather frayed and will have your name sewn in the back by your mum. Steven Chapman Science Year Manager, British Association for the Advancement of Science Signing Off takes a humorous and irreverent look at physics education. The views expressed here are those of the author and are not endorsed by the Editorial Board for Physics Education. Can you contribute a zany attitude or humorous anecdote? Please send your offering to ped@iop.org marked Signing Off.

  5. Infant Sign Training and Functional Analysis

    ERIC Educational Resources Information Center

    Normand, Matthew P.; Machado, Mychal A.; Hustyi, Kristin M.; Morley, Allison J.

    2011-01-01

    We taught manual signs to typically developing infants using a reversal design and caregiver-nominated stimuli. We delivered the stimuli on a time-based schedule during baseline. During the intervention, we used progressive prompting and reinforcement, described by Thompson et al. (2004, 2007), to establish mands. Following sign training, we…

  6. Halo Coronal Mass Ejections and Geomagnetic Storms

    NASA Technical Reports Server (NTRS)

    Gopalswamy, Nat

    2009-01-01

    In this letter, I show that the discrepancies in the geoeffectiveness of halo coronal mass ejections (CMEs) reported in the literature arise due to the varied definitions of halo CMEs used by different authors. In particular, I show that the low geoeffectiveness rate is a direct consequence of including partial halo CMEs. The geoeffectiveness of partial halo CMEs is lower because they are of low speed and likely to make a glancing impact on Earth. Key words: Coronal mass ejections, geomagnetic storms, geoeffectiveness, halo CMEs.

  7. Halo Coronal Mass Ejections and Geomagnetic Storms

    NASA Technical Reports Server (NTRS)

    Gopalswamy, Nat

    2009-01-01

    In this letter, I show that the discrepancies in the geoeffectiveness of halo coronal mass ejections (CMEs) reported in the literature arise due to the varied definitions of halo CMEs used by different authors. In particular, I show that the low geoeffectiveness rate is a direct consequence of including partial halo CMEs. The geoeffectiveness of partial halo CMEs is lower because they are of low speed and likely to make a glancing impact on Earth. Key words: Coronal mass ejections, geomagnetic storms, geoeffectiveness, halo CMEs.

  8. Halo Density Reduction by Baryonic Settling?

    NASA Astrophysics Data System (ADS)

    Jardel, J. R.; Sellwood, J. A.

    2009-02-01

    We test the proposal by El-Zant et al. that the dark matter density of halos could be reduced through dynamical friction acting on heavy baryonic clumps in the early stages of galaxy formation. Using N-body simulations, we confirm that the inner halo density cusp is flattened to 0.2 of the halo break radius by the settling of a single clump of mass gsim0.5% of the halo mass. We also find that an ensemble of 50 clumps, each having masses gsim0.2%, can flatten the cusp to almost the halo break radius on a timescale of ~9 Gyr, for a Navarro-Frenk-White profile halo of concentration 15. We summarize some of the difficulties that need to be overcome if this mechanism is to resolve the apparent conflict between the observed inner densities of galaxy halos and the predictions of ΛCDM.

  9. Ultraviolet Halos around Spiral Galaxies. I. Morphology

    NASA Astrophysics Data System (ADS)

    Hodges-Kluck, Edmund; Cafmeyer, Julian; Bregman, Joel N.

    2016-12-01

    We examine ultraviolet halos around a sample of highly inclined galaxies within 25 Mpc to measure their morphology and luminosity. Despite contamination from galactic light scattered into the wings of the point-spread function, we find that ultraviolet (UV) halos occur around each galaxy in our sample. Around most galaxies the halos form a thick, diffuse disk-like structure, but starburst galaxies with galactic superwinds have qualitatively different halos that are more extensive and have filamentary structure. The spatial coincidence of the UV halos above star-forming regions, the lack of consistent association with outflows or extraplanar ionized gas, and the strong correlation between the halo and galaxy UV luminosity suggest that the UV light is an extragalactic reflection nebula. UV halos may thus represent 106-107 M ⊙ of dust within 2-10 kpc of the disk, whose properties may change with height in starburst galaxies.

  10. Reionization histories of Milky Way mass halos

    SciTech Connect

    Li, Tony Y.; Wechsler, Risa H.; Abel, Tom; Alvarez, Marcelo A. E-mail: rwechsler@stanford.edu E-mail: malvarez@cita.utoronto.ca

    2014-04-20

    We investigate the connection between the reionization era and the present-day universe by examining the mass reionization histories of z = 0 dark matter halos. In a 600{sup 3} Mpc{sup 3} volume, we combine a dark matter N-body simulation with a three-dimensional seminumerical reionization model. This tags each particle with a reionization redshift, so that individual present-day halos can be connected to their reionization histories and environments. We find that the vast majority of present-day halos with masses larger than ∼ few × 10{sup 11} M {sub ☉} reionize earlier than the rest of the universe. We also find significant halo-to-halo diversity in mass reionization histories, and find that in realistic inhomogeneous models, the material within a given halo is not expected to reionize at the same time. In particular, the scatter in reionization times within individual halos is typically larger than the scatter among halos. From our fiducial reionization model, we find that the typical 68% scatter in reionization times within halos is ∼115 Myr for 10{sup 12±0.25} M {sub ☉} halos, decreasing slightly to ∼95 Myr for 10{sup 15±0.25} M {sub ☉} halos. We find a mild correlation between reionization history and environment: halos with shorter reionization histories are typically in more clustered environments, with the strongest trend on a scale of ∼20 Mpc. Material in Milky Way mass halos with short reionization histories is preferentially reionized in relatively large H II regions, implying reionization mostly by sources external to the progenitors of the present-day halo. We investigate the impact on our results of varying the reionization model parameters, which span a range of reionization scenarios with varying timing and morphology.

  11. Clouds Dominate the Galactic Halo

    NASA Astrophysics Data System (ADS)

    2003-01-01

    Using the exquisite sensitivity of the National Science Foundation's Robert C. Byrd Green Bank Telescope (GBT), astronomer Jay Lockman of the National Radio Astronomy Observatory (NRAO) in Green Bank, W. Va., has produced the best cross-section ever of the Milky Way Galaxy's diffuse halo of hydrogen gas. This image confirms the presence of discrete hydrogen clouds in the halo, and could help astronomers understand the origin and evolution of the rarefied atmosphere that surrounds our Galaxy. Lockman presented his findings at the American Astronomical Society meeting in Seattle, WA. Hydrogen Clouds Graphic Artist's Rendering of the Milky Way (background) with insert showing GBT image of cross-section of neutral atomic Hydrogen Credit: Kirk Woellert/National Science Foundation Patricia Smiley, NRAO. "The first observations with the Green Bank Telescope suggested that the hydrogen in the lower halo, the transition zone between the Milky Way and intergalactic space, is very clumpy," said Lockman. "The latest data confirm these results and show that instead of trailing away smoothly from the Galactic plane, a significant fraction of the hydrogen gas in the halo is concentrated in discrete clouds. There are even some filaments." Beyond the star-filled disk of the Milky Way, there exists an extensive yet diffuse halo of hydrogen gas. For years, astronomers have speculated about the origin and structure of this gas. "Even the existence of neutral hydrogen in the halo has been somewhat of a puzzle," Lockman remarked. "Unlike the Earth's atmosphere, which is hot enough to hold itself up against the force of gravity, the hydrogen in the halo is too cool to support itself against the gravitational pull of the Milky Way." Lockman points out that some additional factor has to be involved to get neutral hydrogen to such large distances from the Galactic plane. "This force could be cosmic rays, a supersonic wind, the blast waves from supernovae, or something we have not thought of

  12. Signing off

    NASA Astrophysics Data System (ADS)

    2001-09-01

    Physics Related Aptitude Test As the teacher shortage bites anyone with a degree in science expects to walk into a school and be received, with open arms, as a physics teacher. Are they really suitable? To help you decide Signing Off provides the following invaluable psychometric test. Extensively researched and, for single users only, it comes completely free to Physics Education subscribers! (Copies of this Physics Related Aptitude Test are available to credit-card customers from prat@realripoff.com priced #35 per client, 125 dollars to US customers.) This invaluable psychometric test has been extensively researched. Your first lesson of the new school year introduces the study of electricity. Do you: A Use the notes prepared by your predecessor. B Find a video on electricity and play it to the class. C Arrange a series of exciting practical demonstrations to stimulate the young inquiring mind. D Let the children design and make their own circuits to light flashlight bulbs. Your 14-year-olds have completed a written test on heat and energy. Do you: A Mark correct only the work of students who have written their names neatly at the top LEFT HAND corner, as required. B Only set multiple choice tests, so that the computer can mark them for you. C Mark carefully by hand, explaining in detail to each student exactly how and why they have made errors and adding encouraging comments with lots of praise. D Give out correct sets of answers and allow students to mark their own work. There is a staff social. Do you: A Ask for a definition of the term 'social'. B Ask for a web-based version. C Determine to go, so that you can discuss setting up cross-curricular links with colleagues. D Join the organizing committee. Who do you admire most? A Sir Isaac Newton. B Bill Gates. C Leonardo da Vinci. D Leonardo di Caprio. You are required to teach biology class. Your response is: A Denial. B To ask for an appropriate computer simulation. C To attend a specialized course for biology

  13. Flows of Baryons through the Milky Way Halo

    NASA Astrophysics Data System (ADS)

    Fox, Andrew J.

    2017-07-01

    The Milky Way provides an ideal opportunity to study baryon flows in the circumgalactic medium of a star-forming spiral galaxy. High velocity clouds (HVCs) seen in UV absorption toward background AGN probe the multi-phase ionized gas in the Galactic CGM. In this talk new observations from the Cosmic Origins Spectrograph (COS) on Hubble will be presented, focusing on two Galactic regions: the biconical outflow from the Galactic Center, which drives gas into the Fermi Bubbles, and the Smith Cloud, an accreting HVC close to the Galactic disk showing clear signs of fragmentation. These observations allow us to constrain the rates of gas circulation in the Galactic halo.

  14. The Anemic Stellar Halo of M101

    NASA Astrophysics Data System (ADS)

    Holwerda, Benne

    2014-10-01

    Models of galaxy formation in a cosmological context predict that massive disk galaxies should have richly-structured extended stellar halos, containing ~10% of a galaxy's stars, originating in large part from the tidal disruption of dwarf galaxies. Observations of a number of nearby disk galaxies have generally agreed with these expectations. Recent new observations in integrated light with a novel array of low scattered-light telephoto lenses have failed to convincingly detect a stellar halo in the nearby massive face-on disk galaxy M101 (van Dokkum et al. 2014). They argue that any halo has to have <0.3% of the mass of the galaxy. This halo would be the least massive of any massive disk galaxy in the local Universe (by factors of several) -- such a halo is not predicted or naturally interpreted by the models, and would present a critical challenge to the picture of ubiquitous stellar halos formed from the debris of disrupting dwarf galaxies.We propose to resolve the stellar populations of this uniquely anemic stellar halo for 6 orbits with HST (ACS and WFC3), allowing us to reach surface brightness limits sufficient to clearly detect and characterize M101's stellar halo if it carries more than 0.1% of M101's mass. With resolved stellar populations, we can use the gradient of stellar populations as a function of radius to separate stellar halo from disk, which is impossible using integrated light observations. The resolved stellar populations will reveal the halo mass to much greater accuracy, measure the halo radial profile, constrain any halo lopsidedness, estimate the halo's stellar metallicity, and permit an analysis of outer disk stellar populations.

  15. Halo Microlensing and Dark Baryons

    NASA Astrophysics Data System (ADS)

    Crotts, A. P. S.

    1993-12-01

    (While Pierce lectures review past accomplishments, customarily, this talk concerns efforts which we have pursued for some years and which are now reaching fruition. We present elsewhere at this meeting results from research cited for the Prize.) Dark matter exists in the halos of spiral galaxies, and the least radical alternative for its identity is normal matter produced by primordial nucleosynthesis. This matter could easily be hidden in large, condensed objects. Paczynski pointed out in 1986 that if condensations of Galactic halo matter are sufficiently massive, they will produce detectable amplification of background starlight by gravitational lensing. Several groups recently reported possible detections of this effect after surveying large numbers of stars in the Galactic Bulge and LMC. The connection between these events and massive, dark halos is unclear and likely to remain so for some time, given the rate at which they are detected. Following Paczynski's realization, we stressed that a much higher event rate, a statistical control sample, sensitivity to a much broader mass range, and modulation of the predicted lensing rate with galactocentric distance can all be realized by a different experiment: observing the halo of M31 (and the Galaxy) using stars in M31. In some ways, M31 is a more difficult target than the LMC or the Bulge, given the faintness of its stars, but our observations in 1991 and 1993 indicate that these problems have been surmounted. We can detect stellar variability even under extremely crowded conditions like those in M31's inner disk, and can monitor a sufficient number of stars to study halo lensing. We present results from our initial survey which indicates that the required sensitivity can be reached to confirm or reject the hypothesis that sub-solar masses like those detected in our Galaxy make up the missing spiral galaxy mass. It is possible that we may use the data already obtained (and still being analyzed) to place

  16. The Tully-Fisher and mass-size relations from halo abundance matching

    NASA Astrophysics Data System (ADS)

    Desmond, Harry; Wechsler, Risa H.

    2015-11-01

    The Tully-Fisher relation (TFR) expresses the connection between rotating galaxies and the dark matter haloes they inhabit, and therefore contains a wealth of information about galaxy formation. We construct a general framework to investigate whether models based on halo abundance matching are able to reproduce the observed stellar mass TFR and mass-size relation (MSR), and use the data to constrain galaxy formation parameters. Our model tests a range of plausible scenarios, differing in the response of haloes to disc formation, the relative angular momentum of baryons and dark matter, the impact of selection effects, and the abundance matching parameters. We show that agreement with the observed TFR puts an upper limit on the scatter between galaxy and halo properties, requires weak or reversed halo contraction, and favours selection effects that preferentially eliminate fast-rotating galaxies. The MSR constrains the ratio of the disc to halo specific angular momentum to be approximately in the range 0.6-1.2. We identify and quantify two problems that models of this nature face. (1) They predict too large an intrinsic scatter for the MSR, and (2) they predict too strong an anticorrelation between the TFR and MSR residuals. We argue that resolving these problems requires introducing a correlation between stellar surface density and enclosed dark matter mass. Finally, we explore the expected difference between the TFRs of central and satellite galaxies, finding that in the favoured models this difference should be detectable in a sample of ˜700 galaxies.

  17. Detection of Hot Halo Gets Theory Out of Hot Water

    NASA Astrophysics Data System (ADS)

    2006-02-01

    Scientists using NASA's Chandra X-ray Observatory have detected an extensive halo of hot gas around a quiescent spiral galaxy. This discovery is evidence that galaxies like our Milky Way are still accumulating matter from the gradual inflow of intergalactic gas. "What we are likely witnessing here is the ongoing galaxy formation process," said Kristian Pedersen of the University of Copenhagen, Denmark, and lead author of a report on the discovery. Chandra observations show that the hot halo extends more than 60,000 light years on either side of the disk of the galaxy known as NGC 5746. The detection of such a large halo alleviates a long-standing problem for the theory of galaxy formation. Spiral galaxies are thought to form from enormous clouds of intergalactic gas that collapse to form giant, spinning disks of stars and gas. Chandra X-ray Image of NGC 5746 Chandra X-ray Image of NGC 5746 One prediction of this theory is that large spiral galaxies should be immersed in halos of hot gas left over from the galaxy formation process. Hot gas has been detected around spiral galaxies in which vigorous star formation is ejecting matter from the galaxy, but until now hot halos due to infall of intergalactic matter have not been detected. "Our observations solve the mystery of the missing hot halos around spiral galaxies," said Pedersen. "The halos exist, but are so faint that an extremely sensitive telescope such as Chandra is needed to detect them." DSS Optical Image of NGC 5746 DSS Optical Image of NGC 5746 NGC 5746 is a massive spiral galaxy about a 100 million light years from Earth. Its disk of stars and gas is viewed almost edge-on. The galaxy shows no signs of unusual star formation, or energetic activity from its nuclear region, making it unlikely that the hot halo is produced by gas flowing out of the galaxy. "We targeted NGC 5746 because we thought its distance and orientation would give us the best chance to detect a hot halo caused by the infall of

  18. Historical halo displays as past weather indicator

    NASA Astrophysics Data System (ADS)

    Neuhäuser, Dagmar; Neuhäuser, Ralph

    2017-04-01

    Certain halo displays like the 22° circle were known to indicate specific weather pattern since millennia - as specified in Babylonian omina, Aristotle's Meteorology, farmers' weather lore, etc. Today, it is known that halo phenomena are due to refraction and reflection of sun and moon light in ice crystals in cirrus and cirrostratus, so that halo observations do indicate atmospheric conditions like temperature, humidity, pressure etc. in a few km height. The Astronomical Diaries of Babylonia have recorded both halo phenomena (circles, parhelia, etc.) and weather conditions (rain, clouds, etc.), so that we can use them to show statistically, whether, which and how fast halo phenomena are related to weather - for the last few centuries BC for Babylonia. We can then also compare the observations of Babylonian priests in the given BC epoch (without air and light pollution) with the last few decades of the modern epoch (with air and light pollution), where amateur halo observers have systematically recorded such phenomena (in Europe). Weather and climate are known to be partly driven by solar activity. Hence, one could also consider whether there is an indirect relation between halo displays as weather proxy and aurorae as solar activity proxy - if low solar activity leads to low pressure systems, one could expect more halos, preliminary studies show such a hint. For the last few decades, we have many halo observations, satellite imaging of the aurora oval, and many data on solar activity. A statistically sufficient amount of aurora and halo observations should be available for the historic time to investigate such a possible connection: halos were recorded very often in antiquity and the medieval times (as found in chronicles etc.), and modern scholarly catalogs of aurorae also often contain unrecognized halo displays.

  19. Dark energy and dark matter haloes

    NASA Astrophysics Data System (ADS)

    Kuhlen, Michael; Strigari, Louis E.; Zentner, Andrew R.; Bullock, James S.; Primack, Joel R.

    2005-02-01

    We investigate the effect of dark energy on the density profiles of dark matter haloes with a suite of cosmological N-body simulations and use our results to test analytic models. We consider constant equation of state models, and allow both w>=-1 and w < -1. Using five simulations with w ranging from -1.5 to -0.5, and with more than ~1600 well-resolved haloes each, we show that the halo concentration model of Bullock et al. accurately predicts the median concentrations of haloes over the range of w, halo masses and redshifts that we are capable of probing. We find that the Bullock et al. model works best when halo masses and concentrations are defined relative to an outer radius set by a cosmology-dependent virial overdensity. For a fixed power spectrum normalization and fixed-mass haloes, larger values of w lead to higher concentrations and higher halo central densities, both because collapse occurs earlier and because haloes have higher virial densities. While precise predictions of halo densities are quite sensitive to various uncertainties, we make broad comparisons to galaxy rotation curve data. At fixed power spectrum normalization (fixed σ8), w > -1 quintessence models seem to exacerbate the central density problem relative to the standard w=-1 model. For example, models with w~=- 0.5 seem disfavoured by the data, which can be matched only by allowing extremely low normalizations, σ8<~ 0.6. Meanwhile w < -1 models help to reduce the apparent discrepancy. We confirm that the halo mass function of Jenkins et al. provides an excellent approximation to the abundance of haloes in our simulations and extend its region of validity to include models with w < -1.

  20. Warning Signs After Birth

    MedlinePlus

    ... Home > Pregnancy > Postpartum care > Warning signs after birth Warning signs after birth E-mail to a friend ... breast infection Postpartum bleeding Postpartum depression (PPD) What warning signs should you look for? Call your provider ...

  1. Halo scale predictions of symmetron modified gravity

    SciTech Connect

    Clampitt, Joseph; Jain, Bhuvnesh; Khoury, Justin E-mail: bjain@physics.upenn.edu

    2012-01-01

    We offer predictions of symmetron modified gravity in the neighborhood of realistic dark matter halos. The predictions for the fifth force are obtained by solving the nonlinear symmetron equation of motion in the spherical NFW approximation. In addition, we compare the three major known screening mechanisms: Vainshtein, Chameleon, and Symmetron around such dark matter halos, emphasizing the significant differences between them and highlighting observational tests which exploit these differences. Finally, we demonstrate the host halo environmental screening effect (''blanket screening'') on smaller satellite halos by solving for the modified forces around a density profile which is the sum of satellite and approximate host components.

  2. The total mass of dark matter haloes

    NASA Astrophysics Data System (ADS)

    Anderhalden, Donnino; Diemand, Jürg

    2011-07-01

    The simple, conventional dark matter halo mass definitions commonly used in cosmological simulations ('virial' mass, FoF mass, M50, 100, 200, …) only capture part of the collapsed material and are therefore inconsistent with the halo mass concept used in analytical treatments of structure formation. Simulations have demonstrated that typical dark matter particle orbits extend out to about 90 per cent of their turnaround radius, which results in apocentre passages outside of the current 'virial' radius on the first and also on the second orbit. Here we describe how the formation history of haloes can be used to identify those particles which took part in the halo collapse, but are missed by conventional group finders because of their remote present location. These particles are added to the part of the halo already identified by FoF. The corrected masses of dark haloes are significantly higher (the median mass increase is 25 per cent) and there is a considerable shift of the halo mass function towards the Press and Schechter form. We conclude that meaningful quantitative comparisons between (semi-)analytic predictions of halo properties (e.g. mass functions, mass accretion rates, merger rates, spatial clustering, etc.) and simulation results will require using the same halo definition in both approaches.

  3. Unbound particles in dark matter halos

    SciTech Connect

    Behroozi, Peter S.; Loeb, Abraham; Wechsler, Risa H.

    2013-06-13

    We investigate unbound dark matter particles in halos by tracing particle trajectories in a simulation run to the far future (a = 100). We find that the traditional sum of kinetic and potential energies is a very poor predictor of which dark matter particles will eventually become unbound from halos. We also study the mass fraction of unbound particles, which increases strongly towards the edges of halos, and decreases significantly at higher redshifts. We discuss implications for dark matter detection experiments, precision calibrations of the halo mass function, the use of baryon fractions to constrain dark energy, and searches for intergalactic supernovae.

  4. Progress in understanding halo current at JET

    NASA Astrophysics Data System (ADS)

    Riccardo, V.; Arnoux, G.; Beaumont, P.; Hacquin, S.; Hobirk, J.; Howell, D.; Huber, A.; Joffrin, E.; Koslowski, R.; Lam, N.; Leggate, H.; Rachlew, E.; Sergienko, G.; Stephen, A.; Todd, T.; Zerbini, M.; Delogu, R.; Grando, L.; Marcuzzi, D.; Peruzzo, S.; Pomaro, N.; Sonato, P.; JET EFDA Contributors

    2009-05-01

    The poloidal distribution of the halo current density on the top dump plate in JET can now be measured thanks to a new set of Rogowskii coils. These are the first measurements in JET able to offer an insight in the width of the halo current interaction with the wall. Therefore they offer both validation of the assumption made for JET disruption design criteria and one additional point in the extrapolation of the expected halo current width, and hence halo current density (and related local electro-mechanical loads on in-vessel components) for ITER. During upward events, the measured current density is consistent with the measured total poloidal halo current. The halo footprint extends over most of the upper dump plate, converting to a halo current flux tube width of ~100 mm. A set of four toridal field pick-up coils installed 90° apart now allows a more accurate measurement of the poloidal halo current, in particular its toroidal peaking factor, and direct comparison between halo and plasma asymmetries.

  5. Stellar haloes in Milky Way mass galaxies: from the inner to the outer haloes

    NASA Astrophysics Data System (ADS)

    Tissera, Patricia B.; Beers, Timothy C.; Carollo, Daniela; Scannapieco, Cecilia

    2014-04-01

    We present a comprehensive study of the chemical properties of the stellar haloes of Milky Way mass galaxies, analysing the transition between the inner to the outer haloes. We find the transition radius between the relative dominance of the inner-halo and outer-halo stellar populations to be ˜15-20 kpc for most of our haloes, similar to that inferred for the Milky Way from recent observations. While the number density of stars in the simulated inner-halo populations decreases rapidly with distance, the outer-halo populations contribute about 20-40 per cent in the fiducial solar neighbourhood, in particular at the lowest metallicities. We have determined [Fe/H] profiles for our simulated haloes; they exhibit flat or mild gradients, in the range [-0.002, -0.01] dex kpc-1. The metallicity distribution functions exhibit different features, reflecting the different assembly history of the individual stellar haloes. We find that stellar haloes formed with larger contributions from massive subgalactic systems have steeper metallicity gradients. Very metal-poor stars are mainly contributed to the halo systems by lower mass satellites. There is a clear trend among the predicted metallicity distribution functions that a higher fraction of low-metallicity stars are found with increasing radius. These properties are consistent with the range of behaviours observed for stellar haloes of nearby galaxies.

  6. The Use of Sign Language Pronouns by Native-Signing Children with Autism

    ERIC Educational Resources Information Center

    Shield, Aaron; Meier, Richard P.; Tager-Flusberg, Helen

    2015-01-01

    We report the first study on pronoun use by an under-studied research population, children with autism spectrum disorder (ASD) exposed to American Sign Language from birth by their deaf parents. Personal pronouns cause difficulties for hearing children with ASD, who sometimes reverse or avoid them. Unlike speech pronouns, sign pronouns are…

  7. The Use of Sign Language Pronouns by Native-Signing Children with Autism

    ERIC Educational Resources Information Center

    Shield, Aaron; Meier, Richard P.; Tager-Flusberg, Helen

    2015-01-01

    We report the first study on pronoun use by an under-studied research population, children with autism spectrum disorder (ASD) exposed to American Sign Language from birth by their deaf parents. Personal pronouns cause difficulties for hearing children with ASD, who sometimes reverse or avoid them. Unlike speech pronouns, sign pronouns are…

  8. Haloes seen in UVIS reflectance

    NASA Astrophysics Data System (ADS)

    Esposito, L. W.; Bradley, E. T.; Colwell, J. E.; Sremcevic, M.

    2012-12-01

    UVIS SOI reflectance spectra show bright 'haloes' around the locations of some of the strongest resonances in Saturn's A ring (Esposito etal 2005). UV spectra constrain the size and composition of the icy ring particles (Bradley etal 2010, 2012). We investigate the Janus 4:3, 5:3, 6:5 and Mimas 5:3 inner Lindblad resonances as well as at the Mimas 5:3 vertical resonance (bending wave location). Models of ring particle regolith evolution (Elliott and Esposito 2010) indicate the deeper regolith is made of older and purer ice. The strong resonances can cause streamline crowding (Lewis and Stewart 2005) which damps the interparticle velocity, allowing temporary clumps to grow, which in turn increase the velocity, eroding the clumps and releasing smaller particles and regolith (see the predator-prey model of Esposito etal 2012). This cyclic behavior, driven by the resonant perturbation from the moon, can yield collision velocities at particular azimuths greater than 1m/sec, sufficient to erode the aggregates (Blum 2006), exposing older, purer materials. Thus, the radial location of the strongest resonances can be where we find both large aggregates and disrupted fragments, in a balance maintained by the periodic moon forcing. If this stirring exposes older, and purer ice, the velocity threshold for eroding the aggregates can explain why only the strongest Lindblad resonances show haloes. Diffusion can explain the morphology of these haloes, although they are not well-resolved spatially by UVIS. Spectra determine the relative contributions of particle size and purity at these locations, for comparison to estimates from the regolith evolution models.

  9. The Dual Origin Of Stellar Halos

    NASA Astrophysics Data System (ADS)

    Zolotov, Adi

    In the dominant Lambda+Cold Dark Matter cosmological paradigm, galaxy stellar halos are thought to form hierarchically from multiple accretion events, starting from the first structures to collapse in the Universe. This dissertation aims to make the first detailed theoretical predictions for the origin of galactic stellar halos. We focus on understanding the physical processes involved in halo formation using high-resolution, N-body + Smooth Particle Hydrodynamic simulations of disk galaxies in a cosmological context. These self-consistent simulations are used to study the competing importance of dissipative processes and dissipationless mergers in the formation of stellar halos. The relative contribution of each mechanism, and its specific role in assembling the inner and outer regions of halos is explored, as a function of galaxy mass and merging history. We show that the presence of both accreted and in situ stars in halos is a generic feature of galaxy formation. For L* galaxies, the relative contribution of each stellar population to a halo is shown to be a function of a galaxy's accretion history. Galaxies with recent mergers, like M31, will host relatively few in situ stars, while galaxies with more quiescent recent histories, like the Milky Way, will likely have a larger relative contribution from an in situ population. We show that in situ halo stars are more [alpha/Fe]-rich than accreted stars at the high [Fe/H] end of a halo's metallicity distribution function. In lower mass galaxies, M ˜ 1010 M, in situ stars dominate the stellarmass of halos. In these galaxies, in situ halo stars are, on average, younger and more metal-rich than accreted halo stars. Because in situ stars are dominant, these trends result in halos that are more metal-rich than simple accretion models predict. The halos of low mass galaxies do not extend out to the virial radii of the primary, as they do in more massive galaxies. We find that the ratio of luminous-halo mass to total

  10. THE PSEUDO-EVOLUTION OF HALO MASS

    SciTech Connect

    Diemer, Benedikt; Kravtsov, Andrey V.; More, Surhud

    2013-03-20

    A dark matter halo is commonly defined as a spherical overdensity of matter with respect to a reference density, such as the critical density or the mean matter density of the universe. Such definitions can lead to a spurious pseudo-evolution of halo mass simply due to redshift evolution of the reference density, even if its physical density profile remains constant over time. We estimate the amount of such pseudo-evolution of mass between z = 1 and 0 for halos identified in a large N-body simulation, and show that it accounts for almost the entire mass evolution of the majority of halos with M{sub 200{rho}-bar} Less-Than-Or-Equivalent-To 10{sup 12} h{sup -1} M{sub Sun} and can be a significant fraction of the apparent mass growth even for cluster-sized halos. We estimate the magnitude of the pseudo-evolution assuming that halo density profiles remain static in physical coordinates, and show that this simple model predicts the pseudo-evolution of halos identified in numerical simulations to good accuracy, albeit with significant scatter. We discuss the impact of pseudo-evolution on the evolution of the halo mass function and show that the non-evolution of the low-mass end of the halo mass function is the result of a fortuitous cancellation between pseudo-evolution and the absorption of small halos into larger hosts. We also show that the evolution of the low-mass end of the concentration-mass relation observed in simulations is almost entirely due to the pseudo-evolution of mass. Finally, we discuss the implications of our results for the interpretation of the evolution of various scaling relations between the observable properties of galaxies and galaxy clusters and their halo masses.

  11. Anechoic halo in solid liver tumors: sonographic, microangiographic, and histologic correlation

    SciTech Connect

    Marchal, G.J.; Pylyser, K.; Tshibwabwa-Tumba, E.A.; Verbeken, E.K.; Oyen, R.H.; Baert, A.L.; Lauweryns, J.M.

    1985-08-01

    The origin of the sonographic halo sign in liver metastases was studied after autopsy in 33 livers with macroscopic tumoral involvement. For 20 lesions a detailed comparison of findings from high-resolution 7.5- and 10-MHz sonography, microangiography, and histology was carried out. Histologic study focused on the tumor periphery and its relationship to the adjacent liver parenchyma. In particular, the type of tumor infiltration, the presence or absence of peritumoral fibrosis, and the degree of liver cell compression were assessed. In all but two cases the halo was extratumoral and was caused by peritumoral liver cell compression. In the remaining two cases the halo was tumoral and was caused by irregular fibrosis or vascularization.

  12. HaloSat - A CubeSat to Study the Hot Galactic Halo

    NASA Astrophysics Data System (ADS)

    Kaaret, Philip

    2017-08-01

    Observations of the nearby universe fail to locate about half of the normal matter (baryons) observed in the early universe. The missing baryons may be in hot galactic halos. HaloSat is a CubeSat designed to map oxygen line emission (O VII and O VIII) around the Milky Way in order to constrain the mass and spatial distribution of hot gas in the halo. HaloSat has a grasp competitive with current X-ray observatories. Its observing program will be optimized to minimize contributions from solar wind charge exchange (SWCX) emission that limit the accuracy of current measurements. We describe the current status of HaloSat.

  13. Traumatic atlantoaxial rotatory dislocation and displaced ossiculum terminale epiphysiolysis treated with a halo device: a case report.

    PubMed

    Walbom, Jonas; Kruse, Anders

    2016-07-01

    The horizontal synchondroses of the infant axis are biomechanical weak regions in trauma. We report the case of a 6-year-old girl who presented with delayed atlantoaxial dislocation and displaced ossiculum terminale epiphysiolysis after a fall from a tree. The patient was treated with halo traction for 3 days after which a CT scan showed normal position of the C1/C2 joint, and an acceptable position of the ossiculum terminale whereafter a halo brace was applied. Because of delayed union on CT scans, the treatment was prolonged to a total of 21 weeks. At final follow-up 26 months after halo brace removal, the patient demonstrated normal range of movement of the neck on clinical examination and radiographs of the cervical spine including lateral flexion/extension radiographs showed no sign of instability of the atlantoaxial joint. Conservative treatment with a halo device versus surgical treatment is discussed.

  14. Correlates of Halo Error in Teacher Evaluation.

    ERIC Educational Resources Information Center

    Moritsch, Brian G.; Suter, W. Newton

    1988-01-01

    An analysis of 300 undergraduate psychology student ratings of teachers was undertaken to assess the magnitude of halo error and a variety of rater, ratee, and course characteristics. The raters' halo errors were significantly related to student effort in the course, previous experience with the instructor, and class level. (TJH)

  15. Confounding among Measures of Leniency and Halo.

    ERIC Educational Resources Information Center

    Alliger, George M.; Williams, Kevin J.

    1989-01-01

    The interrelationships among halo and leniency rating errors were examined using simulated rating data. As leniency increased, halo decreased when measured by dimension intercorrelations but increased when measured by standard deviations across dimensions. Implications of these results for the use of the various measures are discussed. (SLD)

  16. Comments on the Measurement of Halo.

    ERIC Educational Resources Information Center

    Fisicaro, Sebastiano A.; Vance, Robert J.

    1994-01-01

    This article presents arguments that the correlation measure "r" of halo is not conceptually more appropriate than the standard deviation (SD) measure. It also describes conditions under which halo effects occur and when the SD and r measures can be used. Neither measure is uniformly superior to the other. (SLD)

  17. Confounding among Measures of Leniency and Halo.

    ERIC Educational Resources Information Center

    Alliger, George M.; Williams, Kevin J.

    1989-01-01

    The interrelationships among halo and leniency rating errors were examined using simulated rating data. As leniency increased, halo decreased when measured by dimension intercorrelations but increased when measured by standard deviations across dimensions. Implications of these results for the use of the various measures are discussed. (SLD)

  18. Comments on the Measurement of Halo.

    ERIC Educational Resources Information Center

    Fisicaro, Sebastiano A.; Vance, Robert J.

    1994-01-01

    This article presents arguments that the correlation measure "r" of halo is not conceptually more appropriate than the standard deviation (SD) measure. It also describes conditions under which halo effects occur and when the SD and r measures can be used. Neither measure is uniformly superior to the other. (SLD)

  19. Correlates of Halo Error in Teacher Evaluation.

    ERIC Educational Resources Information Center

    Moritsch, Brian G.; Suter, W. Newton

    1988-01-01

    An analysis of 300 undergraduate psychology student ratings of teachers was undertaken to assess the magnitude of halo error and a variety of rater, ratee, and course characteristics. The raters' halo errors were significantly related to student effort in the course, previous experience with the instructor, and class level. (TJH)

  20. Analytical halo model of galactic conformity

    NASA Astrophysics Data System (ADS)

    Pahwa, Isha; Paranjape, Aseem

    2017-09-01

    We present a fully analytical halo model of colour-dependent clustering that incorporates the effects of galactic conformity in a halo occupation distribution framework. The model, based on our previous numerical work, describes conformity through a correlation between the colour of a galaxy and the concentration of its parent halo, leading to a correlation between central and satellite galaxy colours at fixed halo mass. The strength of the correlation is set by a tunable 'group quenching efficiency', and the model can separately describe group-level correlations between galaxy colour (1-halo conformity) and large-scale correlations induced by assembly bias (2-halo conformity). We validate our analytical results using clustering measurements in mock galaxy catalogues, finding that the model is accurate at the 10-20 per cent level for a wide range of luminosities and length-scales. We apply the formalism to interpret the colour-dependent clustering of galaxies in the Sloan Digital Sky Survey (SDSS). We find good overall agreement between the data and a model that has 1-halo conformity at a level consistent with previous results based on an SDSS group catalogue, although the clustering data require satellites to be redder than suggested by the group catalogue. Within our modelling uncertainties, however, we do not find strong evidence of 2-halo conformity driven by assembly bias in SDSS clustering.

  1. Milky Way halo gas kinematics

    NASA Technical Reports Server (NTRS)

    Danly, L.

    1986-01-01

    Measurements of high resolution, short wavelength absorption data taken by IUE toward high latitude O and B stars are presented in a discussion of the large scale kinematic properties of Milky Way Halo gas. An analysis of these data demonstrates that: (1) the obsrved absorption widths (FWHM) of Si II are very large, ranging up to 150 Km/s for the most distant halo star; this is much larger than is generally appreciated from optical data; (2) the absorption is observed to be systematically negative in radial velocity, indicating that cool material is, on the whole, flowing toward the disk of the galaxy; (3) there is some evidence for asymmetry between the northern and southern galactic hemispheres, in accordance with the HI 21 cm data toward the galactic poles; (4) low column density gas with highly negative radial LSR velocity (V less than -70 km/s) can be found toward stars beyond 1-3 kpc in the northern galactic hemisphere in all four quadrants of galactic longitude; and (5) only the profiles toward stars in the direction of known high velocity HI features show a clear two component structure.

  2. Probing the galactic halo with ROSAT

    NASA Technical Reports Server (NTRS)

    Burrows, David N.; Mendenhall, J. A.

    1992-01-01

    We discuss the current status of ROSAT shadowing observations designed to search for emission from million degree gas in the halo of the Milky Way galaxy. Preliminary results indicate that million degree halo gas is observed in the 1/4 keV band in some directions, most notably toward the Draco cloud at (l,b) = (92 deg, +38 deg), but that the halo emission is patchy and highly anisotropic. Our current understanding of this halo emission is based on a small handful of observations which have been analyzed to date. Many more observations are currently being analyzed or are scheduled for observation within the next year, and we expect our understanding of this component of the galactic halo to improve dramatically in the near future.

  3. Probing the galactic halo with ROSAT

    NASA Technical Reports Server (NTRS)

    Burrows, D. N.; Mendenhall, J. A.

    1993-01-01

    We discuss the current status of ROSAT shadowing observations designed to search for emission from million degree gas in the halo of the Milky Way galaxy. Preliminary results indicate that million degree halo gas is observed in the 1/4 keV band in some directions, most notably toward the Draco cloud at (l,b) = (92 deg, +38 deg), but that the halo emission is patchy and highly anisotropic. Our current understanding of this halo emission is based on a small handful of observations which have been analyzed to date. Many more observations are currently being analyzed or are scheduled for observation within the next year, and we expect our understanding of this component of the galactic halo to improve dramatically in the near future.

  4. Smooth halos in the cosmic web

    NASA Astrophysics Data System (ADS)

    Gaite, José

    2015-04-01

    Dark matter halos can be defined as smooth distributions of dark matter placed in a non-smooth cosmic web structure. This definition of halos demands a precise definition of smoothness and a characterization of the manner in which the transition from smooth halos to the cosmic web takes place. We introduce entropic measures of smoothness, related to measures of inequality previously used in economy and with the advantage of being connected with standard methods of multifractal analysis already used for characterizing the cosmic web structure in cold dark matter N-body simulations. These entropic measures provide us with a quantitative description of the transition from the small scales portrayed as a distribution of halos to the larger scales portrayed as a cosmic web and, therefore, allow us to assign definite sizes to halos. However, these ``smoothness sizes'' have no direct relation to the virial radii. Finally, we discuss the influence of N-body discreteness parameters on smoothness.

  5. Where have all the cluster halos gone?

    NASA Technical Reports Server (NTRS)

    Burns, Jack O.; Sulkanen, Martin E.; Gisler, Galen R.; Perley, Rick A.

    1992-01-01

    A new LF (330 MHz) VLA image of the Perseus cluster confirms the presence of a miniradio halo with diameter of about 430 kpc (H0 = 75 km/s Mpc) surrounding 3C 84. A careful comparison with the Coma cluster shows that there is no evidence for a similar, very extended halo in Perseus despite the large number of cluster radio galaxies which could power such a halo. These two clusters represent two classes of radio halos which differ by the absence (Coma) or presence (Perseus) of cooling inflows. It is argued that smaller halos as in Perseus result form insufficient clusterwide magnetic fields. A simple model is presented which suggests that cooling flows can suppress the diffusion of turbulently amplified B-fields outward from the cluster core. Such a suppression leads to the development of minihalos which are confined to the cores of cooling flow clusters.

  6. Smooth halos in the cosmic web

    SciTech Connect

    Gaite, José

    2015-04-01

    Dark matter halos can be defined as smooth distributions of dark matter placed in a non-smooth cosmic web structure. This definition of halos demands a precise definition of smoothness and a characterization of the manner in which the transition from smooth halos to the cosmic web takes place. We introduce entropic measures of smoothness, related to measures of inequality previously used in economy and with the advantage of being connected with standard methods of multifractal analysis already used for characterizing the cosmic web structure in cold dark matter N-body simulations. These entropic measures provide us with a quantitative description of the transition from the small scales portrayed as a distribution of halos to the larger scales portrayed as a cosmic web and, therefore, allow us to assign definite sizes to halos. However, these ''smoothness sizes'' have no direct relation to the virial radii. Finally, we discuss the influence of N-body discreteness parameters on smoothness.

  7. Concentrations of Simulated Dark Matter Halos

    NASA Astrophysics Data System (ADS)

    Child, Hillary

    2017-01-01

    We present the concentration-mass (c-M) relation of dark matter halos in two new high-volume high-resolution cosmological N-body simulations, Q Continuum and Outer Rim. Concentration describes the density of the central regions of halos; it is highest for low-mass halos at low redshift, decreasing at high mass and redshift. The shape of the c-M relation is an important probe of cosmology. We discuss the redshift dependence of the c-M relation, several different methods to determine concentrations of simulated halos, and potential sources of bias in concentration measurements. To connect to lensing observations, we stack halos, which also allows us to assess the suitability of the Navarro-Frenk-White profile and other profiles, such as Einasto, with an additional shape parameter. This material is based upon work supported by the National Science Foundation Graduate Research Fellowship under Grant No. DGE-1144082.

  8. Orbital anisotropy in cosmological haloes revisited

    NASA Astrophysics Data System (ADS)

    Wojtak, Radosław; Gottlöber, Stefan; Klypin, Anatoly

    2013-09-01

    The velocity anisotropy of particles inside dark matter (DM) haloes is an important physical quantity, which is required for the accurate modelling of mass profiles of galaxies and clusters of galaxies. It is typically measured using the ratio of the radial to tangential velocity dispersions at a given distance from the halo centre. However, this measure is insufficient to describe the dynamics of realistic haloes, which are not spherical and are typically quite elongated. Studying the velocity distribution in massive DM haloes in cosmological simulations, we find that in the inner parts of the haloes, the local velocity ellipsoids are strongly aligned with the major axis of the halo, the alignment being stronger for more relaxed haloes. In the outer regions of the haloes, the alignment becomes gradually weaker and the orientation is more random. These two distinct regions of different degree of the alignment coincide with two characteristic regimes of the DM density profile: a shallow inner cusp and a steep outer profile that are separated by a characteristic radius at which the density declines as ρ ∝ r-2. This alignment of the local velocity ellipsoids requires reinterpretation of features found in measurements based on the spherically averaged ratio of the radial to tangential velocity dispersions. In particular, we show that the velocity distribution in the central halo regions is highly anisotropic. For cluster-size haloes with mass 1014-1015 h-1 M⊙, the velocity anisotropy along the major axis is nearly independent of radius and is equal to β = 1 - σ ^2_perp/σ ^2_radial≈ 0.4, which is significantly larger than the previously estimated spherically averaged velocity anisotropy. The alignment of density and velocity anisotropies and the radial trends may also have some implications for the mass modelling based on kinematical data of objects such as galaxy clusters or dwarf spheroidals, where the orbital anisotropy is a key element in an unbiased mass

  9. RHAPSODY. I. STRUCTURAL PROPERTIES AND FORMATION HISTORY FROM A STATISTICAL SAMPLE OF RE-SIMULATED CLUSTER-SIZE HALOS

    SciTech Connect

    Wu, Hao-Yi; Hahn, Oliver; Wechsler, Risa H.; Mao, Yao-Yuan; Behroozi, Peter S.

    2013-02-15

    We present the first results from the RHAPSODY cluster re-simulation project: a sample of 96 'zoom-in' simulations of dark matter halos of 10{sup 14.8{+-}0.05} h {sup -1} M {sub Sun }, selected from a 1 h {sup -3} Gpc{sup 3} volume. This simulation suite is the first to resolve this many halos with {approx}5 Multiplication-Sign 10{sup 6} particles per halo in the cluster mass regime, allowing us to statistically characterize the distribution of and correlation between halo properties at fixed mass. We focus on the properties of the main halos and how they are affected by formation history, which we track back to z = 12, over five decades in mass. We give particular attention to the impact of the formation history on the density profiles of the halos. We find that the deviations from the Navarro-Frenk-White (NFW) model and the Einasto model depend on formation time. Late-forming halos tend to have considerable deviations from both models, partly due to the presence of massive subhalos, while early-forming halos deviate less but still significantly from the NFW model and are better described by the Einasto model. We find that the halo shapes depend only moderately on formation time. Departure from spherical symmetry impacts the density profiles through the anisotropic distribution of massive subhalos. Further evidence of the impact of subhalos is provided by analyzing the phase-space structure. A detailed analysis of the properties of the subhalo population in RHAPSODY is presented in a companion paper.

  10. Ophthalmic halo reduced lenses design

    NASA Astrophysics Data System (ADS)

    Limon, Ofer; Zalevsky, Zeev

    2015-05-01

    The halo effect is a very problematic visual artifact occurring in extended depth of focus or multi-focal ophthalmic lenses such as e.g. intra-ocular (after cataract surgery) or contact lenses when used in dark illumination conditions. This artifact is generated due to surface structures added on top of those lenses in order to increase their depth of focus or to realize multiple focal lengths. In this paper we present novel solution that can resolve this major problem of ophthalmic lenses. The proposed solution involves modification to the surface structure that realizes the extended depth of focus. Our solution is fabricated and numerically and experimentally validated also in preliminary in-vivo trials.

  11. NUBEAM developments and 3d halo modeling

    NASA Astrophysics Data System (ADS)

    Gorelenkova, M. V.; Medley, S. S.; Kaye, S. M.

    2012-10-01

    Recent developments related to the 3D halo model in NUBEAM code are described. To have a reliable halo neutral source for diagnostic simulation, the TRANSP/NUBEAM code has been enhanced with full implementation of ADAS atomic physic ground state and excited state data for hydrogenic beams and mixed species plasma targets. The ADAS codes and database provide the density and temperature dependence of the atomic data, and the collective nature of the state excitation process. To be able to populate 3D halo output with sufficient statistical resolution, the capability to control the statistics of fast ion CX modeling and for thermal halo launch has been added to NUBEAM. The 3D halo neutral model is based on modification and extension of the ``beam in box'' aligned 3d Cartesian grid that includes the neutral beam itself, 3D fast neutral densities due to CX of partially slowed down fast ions in the beam halo region, 3D thermal neutral densities due to CX deposition and fast neutral recapture source. More details on the 3D halo simulation design will be presented.

  12. Halo assembly bias from Separate Universe simulations

    NASA Astrophysics Data System (ADS)

    Paranjape, Aseem; Padmanabhan, Nikhil

    2017-07-01

    We present a calibration of halo assembly bias using the Separate Universe technique. Specifically, we measure the response of halo abundances at fixed mass and concentration to the presence of an infinite-wavelength initial perturbation. We develop an analytical framework for describing the concentration dependence of this peak-background split halo bias - a measure of assembly bias - relying on the near-lognormal distribution of halo concentration at fixed halo mass. The combination of this analytical framework and the Separate Universe technique allows us to achieve very high precision in the calibration of the linear assembly bias b1, and qualitatively reproduces known trends such as the monotonic decrease (increase) of b1 with halo concentration at large (small) masses. The same framework extends to the concentration dependence of higher order bias parameters bn, and we present the first calibration of assembly bias in b2. Our calibrations are directly applicable in analytical Halo Model calculations that seek to robustly detect galaxy assembly bias in observational samples. We detect a non-universality in the b1-b2 relation arising from assembly bias, and suggest that simultaneous measurements of these bias parameters could be used to both detect the signature of assembly bias as well as mitigate its effects in cosmological analyses.

  13. Dark matter haloes: a multistream view

    NASA Astrophysics Data System (ADS)

    Ramachandra, Nesar S.; Shandarin, Sergei F.

    2017-09-01

    Mysterious dark matter constitutes about 85 per cent of all masses in the Universe. Clustering of dark matter plays a dominant role in the formation of all observed structures on scales from a fraction to a few hundreds of Mega-parsecs. Galaxies play a role of lights illuminating these structures so they can be observed. The observations in the last several decades have unveiled opulent geometry of these structures currently known as the cosmic web. Haloes are the highest concentrations of dark matter and host luminous galaxies. Currently the most accurate modelling of dark matter haloes is achieved in cosmological N-body simulations. Identifying the haloes from the distribution of particles in N-body simulations is one of the problems attracting both considerable interest and efforts. We propose a novel framework for detecting potential dark matter haloes using the field unique for dark matter-multistream field. The multistream field emerges at the non-linear stage of the growth of perturbations because the dark matter is collisionless. Counting the number of velocity streams in gravitational collapses supplements our knowledge of spatial clustering. We assume that the virialized haloes have convex boundaries. Closed and convex regions of the multistream field are hence isolated by imposing a positivity condition on all three eigenvalues of the Hessian estimated on the smoothed multistream field. In a single-scale analysis of high multistream field resolution and low softening length, the halo substructures with local multistream maxima are isolated as individual halo sites.

  14. Anisotropic halo model: implementation and numerical results

    NASA Astrophysics Data System (ADS)

    Sgró, Mario A.; Paz, Dante J.; Merchán, Manuel

    2013-07-01

    In the present work, we extend the classic halo model for the large-scale matter distribution including a triaxial model for the halo profiles and their alignments. In particular, we derive general expressions for the halo-matter cross-correlation function. In addition, by numerical integration, we obtain instances of the cross-correlation function depending on the directions given by halo shape axes. These functions are called anisotropic cross-correlations. With the aim of comparing our theoretical results with the simulations, we compute averaged anisotropic correlations in cones with their symmetry axis along each shape direction of the centre halo. From these comparisons we characterize and quantify the alignment of dark matter haloes on the Λcold dark matter context by means of the presented anisotropic halo model. Since our model requires multidimensional integral computation we implement a Monte Carlo method on GPU hardware which allows us to increase the precision of the results and it improves the performance of the computation.

  15. Halo bias in mixed dark matter cosmologies

    NASA Astrophysics Data System (ADS)

    LoVerde, Marilena

    2014-10-01

    The large-scale distribution of cold dark matter halos is generally assumed to trace the large-scale distribution of matter. In a universe with multiple types of matter fluctuations, as is the case with massive neutrinos, the relation between the halo field and the matter fluctuations may be more complicated. We develop a method for calculating the linear bias factor relating fluctuations in the halo number density to fluctuations in the mass density in the presence of multiple fluctuating components of the energy density. In the presence of massive neutrinos we find a small but pronounced feature in the halo bias near the neutrino free-streaming scale. The neutrino feature is a small step with amplitude that increases with halo mass and neutrino mass density. The scale-dependent halo bias lessens the suppression of the small-scale halo power spectrum and should therefore weaken constraints on neutrino mass from the galaxy autopower spectrum and correlation function. On the other hand, the feature in the bias is itself a novel signature of massive neutrinos that can be studied independently.

  16. Population Gradients in Stellar Halos from GHOSTS

    NASA Astrophysics Data System (ADS)

    Bailin, Jeremy; Monachesi, Antonela; Bell, Eric F.; de Jong, Roelof S.; Ghosts Survey

    2015-01-01

    We report on recent results from the Galaxy Halos, Outer disks, Substructure, Thick disks, and Star clusters (GHOSTS) survey, an HST ACS+WFC3 imaging survey to study stellar populations in and around 16 nearby spiral galaxies. By using HST resolution to resolve the stellar halos into individual red giant branch (RGB) stars, we are able to detect distinct stellar populations at several points throughout the halo of the half dozen massive highly-inclined galaxies in the sample. In approximately half of these galaxies, we detect a gradient in the color of the RGB; which we interpret as a metallicity gradient. Stellar halo formation models predict a wide variety of metallicity gradients: those in which the halos are dominated by stars formed in situ predict stronger gradients than we observe, while accretion-dominated halo models predict weaker or nonexistent gradients. Our measurements therefore provide a useful discriminator between stellar halo models, and at first look appear most consistent with the accretion-based model of Cooper et al. (2010).

  17. THE DUAL ORIGIN OF STELLAR HALOS

    SciTech Connect

    Zolotov, Adi; Hogg, David W.; Willman, Beth; Brooks, Alyson M.; Brook, Chris B.; Stinson, Greg E-mail: bwillman@haverford.edu

    2009-09-10

    We investigate the formation of the stellar halos of four simulated disk galaxies using high-resolution, cosmological SPH + N-body simulations. These simulations include a self-consistent treatment of all the major physical processes involved in galaxy formation. The simulated galaxies presented here each have a total mass of {approx}10{sup 12} M{sub sun}, but span a range of merger histories. These simulations allow us to study the competing importance of in situ star formation (stars formed in the primary galaxy) and accretion of stars from subhalos in the building of stellar halos in a {lambda}CDM universe. All four simulated galaxies are surrounded by a stellar halo, whose inner regions (r < 20 kpc) contain both accreted stars, and an in situ stellar population. The outer regions of the galaxies' halos were assembled through pure accretion and disruption of satellites. Most of the in situ halo stars formed at high redshift out of smoothly accreted cold gas in the inner 1 kpc of the galaxies' potential wells, possibly as part of their primordial disks. These stars were displaced from their central locations into the halos through a succession of major mergers. We find that the two galaxies with recently quiescent merger histories have a higher fraction of in situ stars ({approx}20%-50%) in their inner halos than the two galaxies with many recent mergers ({approx}5%-10% in situ fraction). Observational studies concentrating on stellar populations in the inner halo of the Milky Way will be the most affected by the presence of in situ stars with halo kinematics, as we find that their existence in the inner few tens of kpc is a generic feature of galaxy formation.

  18. The Dual Origin of Galactic Stellar Halos

    NASA Astrophysics Data System (ADS)

    Zolotov, Adi

    2011-01-01

    Accreted stellar halos are a natural consequence of galaxy formation in a Lambda-CDM Universe, and contain unique fossil records of hierarchical galaxy formation. The properties of local Milky Way halo stars, however, suggest that the Galaxy's halo is composed of at least two distinct stellar populations, each exhibiting different spatial distributions, orbits, and metallicities. This observed dichotomy is the result of the assembly history of the halo, which likely formed through a process more complex than pure hierarchical accretions. In this talk I will describe the formation of stellar halos surrounding Milky Way-massed disk galaxies simulated using high-resolution cosmological Smooth Particle Hydrodynamics + N-Body simulations. We find that two competing physical processes - accretion of dwarf galaxies and in situ star formation - contribute to the formation of every stellar halo. While the outer regions (r > 20 kpc) of the halos were assembled solely through the accretion and disruption of satellites, in situ star formation supplements accretion in the formation of inner halos. The relative contribution of each stellar population to a halo is shown to be a function of a galaxy's merging history. Galaxies with recent mergers, like M31, will host relatively few in situ stars, while galaxies with more quiescent recent histories, like the Milky Way, will likely have a larger population of such stars. We show how the chemical abundance trends ([Fe/H] vs. [alpha/Fe]) of accreted and in situ stars diverge at the high [Fe/H] end of the metallicity distribution function, and discuss how such trends can be used to study and identify the observable imprints of the Milky Way's formation history.

  19. Effective field theory description of halo nuclei

    NASA Astrophysics Data System (ADS)

    Hammer, H.-W.; Ji, C.; Phillips, D. R.

    2017-10-01

    Nuclear halos emerge as new degrees of freedom near the neutron and proton driplines. They consist of a core and one or a few nucleons which spend most of their time in the classically-forbidden region outside the range of the interaction. Individual nucleons inside the core are thus unresolved in the halo configuration, and the low-energy effective interactions are short-range forces between the core and the valence nucleons. Similar phenomena occur in clusters of 4He atoms, cold atomic gases near a Feshbach resonance, and some exotic hadrons. In these weakly-bound quantum systems universal scaling laws for s-wave binding emerge that are independent of the details of the interaction. Effective field theory (EFT) exposes these correlations and permits the calculation of non-universal corrections to them due to short-distance effects, as well as the extension of these ideas to systems involving the Coulomb interaction and/or binding in higher angular-momentum channels. Halo nuclei exhibit all these features. Halo EFT, the EFT for halo nuclei, has been used to compute the properties of single-neutron, two-neutron, and single-proton halos of s-wave and p-wave type. This review summarizes these results for halo binding energies, radii, Coulomb dissociation, and radiative capture, as well as the connection of these properties to scattering parameters, thereby elucidating the universal correlations between all these observables. We also discuss how Halo EFT's encoding of the long-distance physics of halo nuclei can be used to check and extend ab initio calculations that include detailed modeling of their short-distance dynamics.

  20. COSMIC VORTICITY AND THE ORIGIN HALO SPINS

    SciTech Connect

    Libeskind, Noam I.; Steinmetz, Matthias; Gottloeber, Stefan; Hess, Steffen; Hoffman, Yehuda; Knebe, Alexander

    2013-04-01

    In the standard model of cosmology, structure emerges out of a non-rotational flow and the angular momentum of collapsing halos is induced by tidal torques. The growth of angular momentum in the linear and quasi-linear phases is associated with a shear, curl-free, flow and it is well described within the linear framework of tidal torque theory (TTT). However, TTT ceases to be applicable as halos approach turnaround when their ambient flow field becomes rotational. Subsequently, halos become embedded in a vortical flow field and the growth of their angular momentum is affected by the vorticity of their ambient velocity field. Using a cosmological simulation, we have examined the importance of the curl of the velocity field in determining halo spin, finding a significant alignment between the two: the vorticity tends to be perpendicular to the axis of the fastest collapse of the velocity shear tensor (e{sub 1}). This is independent of halo masses and cosmic web environment. Our results agree with previous findings on the tendency of halo spin to be perpendicular to e{sub 1}, and of the spin of (simulated) halos and (observed) galaxies to be aligned with the large-scale structure. It follows that angular momentum growth proceeds in two distinct phases. First, the angular momentum emerges out of a shear, curl-free, potential flow, as described by TTT. In the second phase, in which halos approach virialization, the angular momentum emerges out of a vortical flow and halo spin becomes partially aligned with the vorticity of the ambient flow field.

  1. DARK MATTER HALO PROFILES OF MASSIVE CLUSTERS: THEORY VERSUS OBSERVATIONS

    SciTech Connect

    Bhattacharya, Suman; Habib, Salman; Heitmann, Katrin; Vikhlinin, Alexey

    2013-03-20

    Dark-matter-dominated cluster-scale halos act as an important cosmological probe and provide a key testing ground for structure formation theory. Focusing on their mass profiles, we have carried out (gravity-only) simulations of the concordance {Lambda}CDM cosmology, covering a mass range of 2 Multiplication-Sign 10{sup 12} to 2 Multiplication-Sign 10{sup 15} h {sup -1} M{sub Sun} and a redshift range of z = 0-2, while satisfying the associated requirements of resolution and statistical control. When fitting to the Navarro-Frenk-White profile, our concentration-mass (c-M) relation differs in normalization and shape in comparison to previous studies that have limited statistics in the upper end of the mass range. We show that the flattening of the c-M relation with redshift is naturally expressed if c is viewed as a function of the peak height parameter, {nu}. Unlike the c-M relation, the slope of the c-{nu} relation is effectively constant over the redshift range z = 0-2, while the amplitude varies by {approx}30% for massive clusters. This relation is, however, not universal: using a simulation suite covering the allowed wCDM parameter space, we show that the c-{nu} relation varies by about {+-}20% as cosmological parameters are varied. At fixed mass, the c(M) distribution is well fit by a Gaussian with {sigma}{sub c}/(c) {approx_equal} 1/3, independent of the radius at which the concentration is defined, the halo dynamical state, and the underlying cosmology. We compare the {Lambda}CDM predictions with observations of halo concentrations from strong lensing, weak lensing, galaxy kinematics, and X-ray data, finding good agreement for massive clusters (M{sub vir} > 4 Multiplication-Sign 10{sup 14} h {sup -1} M{sub Sun }), but with some disagreements at lower masses. Because of uncertainty in observational systematics and modeling of baryonic physics, the significance of these discrepancies remains unclear.

  2. The statistics of Λ CDM halo concentrations

    NASA Astrophysics Data System (ADS)

    Neto, Angelo F.; Gao, Liang; Bett, Philip; Cole, Shaun; Navarro, Julio F.; Frenk, Carlos S.; White, Simon D. M.; Springel, Volker; Jenkins, Adrian

    2007-11-01

    We use the Millennium Simulation (MS) to study the statistics of Λ cold dark matter (ΛCDM) halo concentrations at z = 0. Our results confirm that the average halo concentration declines monotonically with mass; the concentration-mass relation is well fitted by a power law over three decades in mass, up to the most massive objects that form in a ΛCDM universe (~ 1015h-1Msolar). This is in clear disagreement with the predictions of the model proposed by Bullock et al. for these rare objects, and agrees better with the original predictions of Navarro, Frenk & White. The large volume surveyed, together with the unprecedented numerical resolution of the MS, allows us to estimate with confidence the distribution of concentrations and, consequently, the abundance of systems with unusual properties. About one in a hundred cluster haloes (M200 >~ 3 × 1014h-1Msolar) have concentrations exceeding c200 = 7.5, a result that may be useful in interpreting the likelihood of unusually strong massive gravitational lenses, such as Abell 1689, in the ΛCDM cosmogony. A similar fraction of about 1 per cent of galaxy-sized haloes (M200 ~ 1012h-1Msolar) have c200 < 4.5 and this could be relevant to models that attempt to reconcile the ΛCDM cosmology with rotation curves of low surface brightness galaxies by appealing to haloes of unexpectedly low concentration. We find that halo concentrations are independent of spin once haloes manifestly out of equilibrium have been removed from the sample. Compared to their relaxed brethren, the concentrations of out-of-equilibrium haloes tend to be lower and have more scatter, while their spins tend to be higher. A number of previously noted trends within the halo population are induced primarily by these properties of unrelaxed systems. Finally, we compare the result of predicting halo concentrations using the mass assembly history of the main progenitor with predictions based on simple arguments regarding the assembly time of all progenitors

  3. Halo Mergers in Phase-space

    NASA Astrophysics Data System (ADS)

    Taylor, J. E.

    I consider a very simple model for the evolution of the real space and phase-space density profiles of a dark matter halo as it acquires its mass. I show that this model, which assumes slow growth through gradual accretion, predicts structures much more concentrated than those found in self-consistent simulations of halo formation. By implication, major mergers must act to reduce the concentration of dark matter haloes, adding the orbital energy of the infalling satellite to the internal energy of the pre-existing system and causing it to expand at intermediate radii. This effect should be easy to detect in numerical simulations.

  4. Haloes around the Moon and the Sun

    NASA Astrophysics Data System (ADS)

    Gaina, Alex; Gaina, Danielle A.

    2008-10-01

    The authors observations of the Haloes around the Moon and the Sun during few last years are reported. A Historical review of the phenomenon is given since the observations by Benvenuto Cellini and Gaston Tissandier is given. A photograph (from eight available) of the Halo around the Sun observed in Chisinau on 21 May 2007 is included. The Halo from 21 May 2007 occured after a very fast increasing of the air temperature during one day by more than 15 Deg. The authors consider, that the phenomenon is due to scattering of light on Cirri clouds(7 km altitude), present on the sky during that day. They formed due to very fast heating.

  5. Warning Signs of Bullying

    MedlinePlus

    ... to talk to kids about bullying. Respond to Bullying Learn how to respond to bullying . From stopping ... Text Size: A A A Warning Signs for Bullying There are many warning signs that may indicate ...

  6. British Sign Name Customs

    ERIC Educational Resources Information Center

    Day, Linda; Sutton-Spence, Rachel

    2010-01-01

    Research presented here describes the sign names and the customs of name allocation within the British Deaf community. While some aspects of British Sign Language sign names and British Deaf naming customs differ from those in most Western societies, there are many similarities. There are also similarities with other societies outside the more…

  7. Warning Signs After Birth

    MedlinePlus

    ... what moms and moms-to-be need to know GO donate sign-up sign-in Sign out account center dashboard Our Cause Our mission Fighting premature birth About us Annual report Our work Community impact Global programs Research Need help? Frequently asked questions Contact us Tools & ...

  8. British Sign Name Customs

    ERIC Educational Resources Information Center

    Day, Linda; Sutton-Spence, Rachel

    2010-01-01

    Research presented here describes the sign names and the customs of name allocation within the British Deaf community. While some aspects of British Sign Language sign names and British Deaf naming customs differ from those in most Western societies, there are many similarities. There are also similarities with other societies outside the more…

  9. On the System of Person-Denoting Signs in Estonian Sign Language: Estonian Name Signs

    ERIC Educational Resources Information Center

    Paales, Liina

    2010-01-01

    This article discusses Estonian personal name signs. According to study there are four personal name sign categories in Estonian Sign Language: (1) arbitrary name signs; (2) descriptive name signs; (3) initialized-descriptive name signs; (4) loan/borrowed name signs. Mostly there are represented descriptive and borrowed personal name signs among…

  10. On the System of Person-Denoting Signs in Estonian Sign Language: Estonian Name Signs

    ERIC Educational Resources Information Center

    Paales, Liina

    2010-01-01

    This article discusses Estonian personal name signs. According to study there are four personal name sign categories in Estonian Sign Language: (1) arbitrary name signs; (2) descriptive name signs; (3) initialized-descriptive name signs; (4) loan/borrowed name signs. Mostly there are represented descriptive and borrowed personal name signs among…

  11. The Use of Sign Language Pronouns by Native-Signing Children with Autism

    PubMed Central

    Shield, Aaron; Meier, Richard P.; Tager-Flusberg, Helen

    2015-01-01

    We report the first study on pronoun use by an under-studied research population, children with autism spectrum disorder (ASD) exposed to American Sign Language (ASL) from birth by their deaf parents. Personal pronouns cause difficulties for hearing children with ASD, who sometimes reverse or avoid them. Unlike speech pronouns, sign pronouns are indexical points to self and other. Despite this transparency, we find evidence from an elicitation task and parental report that signing children with ASD avoid sign pronouns in favor of names. An analysis of spontaneous usage showed that all children demonstrated the ability to point, but only children with better-developed sign language produced pronouns. Differences in language abilities and self-representation may explain these phenomena in sign and speech. PMID:25643865

  12. The Use of Sign Language Pronouns by Native-Signing Children with Autism.

    PubMed

    Shield, Aaron; Meier, Richard P; Tager-Flusberg, Helen

    2015-07-01

    We report the first study on pronoun use by an under-studied research population, children with autism spectrum disorder (ASD) exposed to American Sign Language from birth by their deaf parents. Personal pronouns cause difficulties for hearing children with ASD, who sometimes reverse or avoid them. Unlike speech pronouns, sign pronouns are indexical points to self and other. Despite this transparency, we find evidence from an elicitation task and parental report that signing children with ASD avoid sign pronouns in favor of names. An analysis of spontaneous usage showed that all children demonstrated the ability to point, but only children with better-developed sign language produced pronouns. Differences in language abilities and self-representation may explain these phenomena in sign and speech.

  13. Dwarf galaxies in the halo of NGC 891

    SciTech Connect

    Schulz, Earl

    2014-07-20

    We report the results of a survey of the region within 40 arcmin of NGC 891, a nearby nearly perfectly edge-on spiral galaxy. Candidate 'non-stars' with diameters greater than 15 arcsec were selected from the GSC 2.3.2 catalog and cross-comparison of observations in several bands using archived GALEX, DSS2, WISE, and Two Micron All Sky Survey images identified contaminating stars, artifacts, and background galaxies, all of which were excluded. The resulting 71 galaxies, many of which were previously uncataloged, comprise a size-limited survey of the region. A majority of the galaxies are in the background of NGC 891 and are for the most part members of the A347 cluster at a distance of about 75 Mpc. The new finds approximately double the known membership of A347, previously thought to be relatively sparse. We identify a total of seven dwarf galaxies, most of which are new discoveries. The newly discovered dwarf galaxies are dim and gas-poor and may be associated with the previously observed arcs of red giant branch halo stars in the halo and the prominent H I filament and the lopsided features in the disk of NGC 891. Several of the dwarfs show signs of disruption, consistent with being remnants of an ancient collision.

  14. Charge form factors of two-neutron halo nuclei in halo EFT

    NASA Astrophysics Data System (ADS)

    Hagen, P.; Hammer, H.-W.; Platter, L.

    2013-09-01

    We set up a formalism to calculate the charge form factors of two-neutron halo nuclei with S -wave neutron-core interactions in the framework of the halo effective field theory. The method is applied to some known and suspected halo nuclei. In particular, we calculate the form factors and charge radii relative to the core to leading order in the halo EFT and compare to experiments where they are available. Moreover, we investigate the general dependence of the charge radius on the core mass and the one- and two-neutron separation energies.

  15. Dark matter particles in the galactic halo

    SciTech Connect

    Bernabei, R. Belli, P.; Montecchia, F.; Nozzoli, F.; Cappella, F.; D'Angelo, A.; Incicchitti, A.; Prosperi, D.; Cerulli, R.; Dai, C. J.; He, H. L.; Kuang, H. H.; Ma, J. M.; Sheng, X. D.; Ye, Z. P.

    2009-12-15

    Arguments on the investigation of the DarkMatter particles in the galactic halo are addressed. Recent results obtained by exploiting the annual modulation signature are summarized and the perspectives are discussed.

  16. Studying stellar halos with future facilities

    NASA Astrophysics Data System (ADS)

    Greggio, Laura; Falomo, Renato; Uslenghi, Michela

    2016-08-01

    Stellar halos around galaxies retain fundamental evidence of the processes which lead to their build up. Sophisticated models of galaxy formation in a cosmological context yield quantitative predictions about various observable characteristics, including the amount of substructure, the slope of radial mass profiles and three dimensional shapes, and the properties of the stellar populations in the halos. The comparison of such models with the observations provides constraints on the general picture of galaxy formation in the hierarchical Universe, as well as on the physical processes taking place in the halos formation. With the current observing facilities, stellar halos can be effectively probed only for a limited number of nearby galaxies. In this paper we illustrate the progress that we expect in this field with the future ground based large aperture telescopes (E-ELT) and with space based facilities as JWST.

  17. Quantum Halo States in Helium Tetramers.

    PubMed

    Stipanović, Petar; Vranješ Markić, Leandra; Boronat, Jordi

    2017-01-12

    The universality of quantum halo states enables a comparison of systems from different fields of physics, as demonstrated in two- and three-body clusters. In the present work, we studied weakly bound helium tetramers in order to test whether some of these four-body realistic systems qualify as halos. Their ground-state binding energies and structural properties were thoroughly estimated using the diffusion Monte Carlo method with pure estimators. Helium tetramer properties proved to be less sensitive on the potential model than previously evaluated trimer properties. We predict the existence of realistic four-body halo (4)He2(3)He2, whereas (4)He4 and (4)He3(3)He are close to the border and thus can be used as prototypes of quasi-halo systems. Our results could be tested by the experimental determination of the tetramers' structural properties using a setup similar to the one developed for the study of helium trimers.

  18. Genesis Halo Orbit Station Keeping Design

    NASA Technical Reports Server (NTRS)

    Lo, M.; Williams, K.; Wilson, R.; Howell, K.; Barden, B.

    2000-01-01

    As the fifth mission of NASA's Directory Program, Genesis is designed to collect solar wind samples for approximately two years in a halo orbit near the Sun-Earth L(sub 1) Lagrange point for return to the Earth.

  19. Genesis Halo Orbit Station Keeping Design

    NASA Technical Reports Server (NTRS)

    Lo, M.; Williams, K.; Wilson, R.; Howell, K.; Barden, B.

    2000-01-01

    As the fifth mission of NASA's Directory Program, Genesis is designed to collect solar wind samples for approximately two years in a halo orbit near the Sun-Earth L(sub 1) Lagrange point for return to the Earth.

  20. Large Halos of Missing Baryons Around Galaxies

    NASA Astrophysics Data System (ADS)

    Bregman, Joel

    2009-10-01

    If galaxies had the cosmological baryon-to-dark matter ratio, they would have 3-30 times their observed baryon mass. These missing baryons are undetected, but some fraction may surround a galaxy with a hot diffuse halo extending to R_virial (250 kpc). A loosely bound gaseous halo could be stripped in a cluster or group environment, but should be relatively undisturbed around isolated late-type spirals. Existing observations of spirals are mainly of nearby systems, where only the inner parts fit in a field of view so a halo on the scale of R_virial would pass unnoticed. To detect or place limits on a large halo of missing baryons, we propose to observe isolated L* spirals sufficiently distant that we can detect emission to at least R_virial.

  1. The Vertical Structure of the Halo Rotation

    NASA Astrophysics Data System (ADS)

    Kinman, T. D.; Cacciari, C.; Bragaglia, A.; Buzzoni, A.; Spagna, A.

    New GSC-II proper motions of RR Lyrae and Blue Horizontal Branch (BHB) stars near the North Galactic Pole are used to show that the Galactic Halo 5 kpc above the Plane has a significantly retrograde galactic rotation.

  2. Solar Back-sided Halo CME

    NASA Image and Video Library

    The Sun erupted with several CMEs (coronal mass ejections) during a period just over a day (Nov. 8-9, 2012), the largest of which was a halo CME. This CME appears to have originated from an active ...

  3. Foxp3(+) regulatory T cells are increased in the early stages of halo nevi: clinicopathological features of 30 halo nevi.

    PubMed

    Park, H S; Jin, S A; Choi, Y-D; Shin, M-H; Lee, S E; Yun, S J

    2012-01-01

    There have been few clinical studies of the role of regulatory T cells (Tregs) in halo formation of halo nevus. To evaluate the clinicopathologic features and the presence of Tregs in halo nevi. We analyzed 30 halo nevi and performed immunohistochemical analysis using antibodies against CD4, CD8, CD25 and Foxp3. We also performed double immunohistochemical staining for Foxp3 and CD25. We found significant increases in Foxp3(+) Tregs, and the shorter the halo nevus duration, the more Foxp3(+) Tregs were detected. Also, the ratio of Foxp3 to CD8 T cells was increased in early stages of halo nevi. Double immunohistochemical staining suggested that the Tregs in the halo nevi were CD25(+)Foxp3(+) T cells. Foxp3(+) Tregs were greatly increased in the halo nevi. The shorter the halo nevi duration, the more Foxp3(+) Tregs were involved in the earlier developmental stages of halo nevi. Copyright © 2012 S. Karger AG, Basel.

  4. Contribution of globular clusters to halos

    NASA Astrophysics Data System (ADS)

    Bragaglia, Angela

    2017-03-01

    The contribution of massive star clusters to their hosting halo dramatically depends on their formation mechanism and their early evolution. Massive globular clusters in the Milky Way (and in other galaxies) have been shown to display peculiar chemical patterns (light-elements correlations and anti-correlations) indicative of a complex star formation, confirmed by photometric evidence (spread or split sequences). I use these chemical signatures to try to understand what is the fraction of halo stars originally born in globular clusters.

  5. On physical scales of dark matter halos

    SciTech Connect

    Zemp, Marcel

    2014-09-10

    It is common practice to describe formal size and mass scales of dark matter halos as spherical overdensities with respect to an evolving density threshold. Here, we critically investigate the evolutionary effects of several such commonly used definitions and compare them to the halo evolution within fixed physical scales as well as to the evolution of other intrinsic physical properties of dark matter halos. It is shown that, in general, the traditional way of characterizing sizes and masses of halos dramatically overpredicts the degree of evolution in the last 10 Gyr, especially for low-mass halos. This pseudo-evolution leads to the illusion of growth even though there are no major changes within fixed physical scales. Such formal size definitions also serve as proxies for the virialized region of a halo in the literature. In general, those spherical overdensity scales do not coincide with the virialized region. A physically more precise nomenclature would be to simply characterize them by their very definition instead of calling such formal size and mass definitions 'virial'. In general, we find a discrepancy between the evolution of the underlying physical structure of dark matter halos seen in cosmological structure formation simulations and pseudo-evolving formal virial quantities. We question the importance of the role of formal virial quantities currently ubiquitously used in descriptions, models, and relations that involve properties of dark matter structures. Concepts and relations based on pseudo-evolving formal virial quantities do not properly reflect the actual evolution of dark matter halos and lead to an inaccurate picture of the physical evolution of our universe.

  6. [Computerizing the radiological sign].

    PubMed

    Bertaud, V; Belhadj, I; Dameron, O; Garcelon, N; Hendaoui, L; Marin, F; Duvauferrier, R

    2007-01-01

    The goal of this article is to present to the radiologist the different theories of the sign and their consequences for sign representation in computer systems. All the theories of the sign are presented, but the most relevant are highlighted in order to explain the great modeling systems currently in use (such as DICOM-SR or the UMLS). The constructivist approach of the notion of disease, the semiosis process, which starting from signs produces new signs, and the structuralist analysis of sign through language are emphasized. The purpose of this analysis is to end up with a consensual representation of the sign that can be understood by human beings and processed by machines. Such a representation, also known as an ontology, is based on a semantic organization of language, thus allowing medicine to become a truly scientific discipline. It aims at disambiguating the symbols given to machines, which will help us in our reasoning.

  7. Sign language Web pages.

    PubMed

    Fels, Deborah I; Richards, Jan; Hardman, Jim; Lee, Daniel G

    2006-01-01

    The WORLD WIDE WEB has changed the way people interact. It has also become an important equalizer of information access for many social sectors. However, for many people, including some sign language users, Web accessing can be difficult. For some, it not only presents another barrier to overcome but has left them without cultural equality. The present article describes a system that allows sign language-only Web pages to be created and linked through a video-based technique called sign-linking. In two studies, 14 Deaf participants examined two iterations of signlinked Web pages to gauge the usability and learnability of a signing Web page interface. The first study indicated that signing Web pages were usable by sign language users but that some interface features required improvement. The second study showed increased usability for those features; users consequently couldnavigate sign language information with ease and pleasure.

  8. ANGULAR MOMENTUM ACQUISITION IN GALAXY HALOS

    SciTech Connect

    Stewart, Kyle R.; Brooks, Alyson M.; Bullock, James S.; Maller, Ariyeh H.; Diemand, Juerg; Wadsley, James; Moustakas, Leonidas A.

    2013-05-20

    We use high-resolution cosmological hydrodynamic simulations to study the angular momentum acquisition of gaseous halos around Milky-Way-sized galaxies. We find that cold mode accreted gas enters a galaxy halo with {approx}70% more specific angular momentum than dark matter averaged over cosmic time (though with a very large dispersion). In fact, we find that all matter has a higher spin parameter when measured at accretion than when averaged over the entire halo lifetime, and is well characterized by {lambda} {approx} 0.1, at accretion. Combined with the fact that cold flow gas spends a relatively short time (1-2 dynamical times) in the halo before sinking to the center, this naturally explains why cold flow halo gas has a specific angular momentum much higher than that of the halo and often forms ''cold flow disks.'' We demonstrate that the higher angular momentum of cold flow gas is related to the fact that it tends to be accreted along filaments.

  9. New views of the distant stellar halo

    NASA Astrophysics Data System (ADS)

    Sanderson, Robyn E.; Secunda, Amy; Johnston, Kathryn V.; Bochanski, John J.

    2017-10-01

    Currently, only a small number of Milky Way (MW) stars are known to exist beyond 100 kpc from the Galactic Centre. Though the distribution of these stars in the outer halo is believed to be sparse, they can provide evidence of more recent accretion events than in the inner halo and help map out the MW's dark matter halo to its virial radius. We have re-examined the outermost regions of 11 existing stellar halo models with two synthetic surveys: one mimicking present-day searches for distant M giants and another mimicking RR Lyra (RRL) projections for the Large Synoptic Survey Telescope (LSST). Our models suggest that colour and proper motion cuts currently used to select M giant candidates for follow-up successfully remove nearly all self-contamination from foreground halo dwarf stars and are useful for focusing observations on distant M giants, of which there are thousands to tens of thousands beyond 100 kpc in our models. We likewise expect that LSST will identify comparable numbers of RRLe at these distances. We demonstrate that several observable properties of both tracers, such as proximity of neighbouring stars, proper motions and distances (for RRLe), could help us separate different accreted dwarf galaxies from one another in the distant MW halo. We also discuss prospects for using ratios of M giants to RRLe as a proxy for accretion time, which in the future could provide new constraints on the recent accretion history of our Galaxy.

  10. MODIFIED GRAVITY SPINS UP GALACTIC HALOS

    SciTech Connect

    Lee, Jounghun; Zhao, Gong-Bo; Li, Baojiu; Koyama, Kazuya

    2013-01-20

    We investigate the effect of modified gravity on the specific angular momentum of galactic halos by analyzing the halo catalogs at z = 0 from high-resolution N-body simulations for a f(R) gravity model that meets the solar-system constraint. It is shown that the galactic halos in the f(R) gravity model tend to acquire significantly higher specific angular momentum than those in the standard {Lambda}CDM model. The largest difference in the specific angular momentum distribution between these two models occurs for the case of isolated galactic halos with mass less than 10{sup 11} h {sup -1} M {sub Sun }, which are likely least shielded by the chameleon screening mechanism. As the specific angular momentum of galactic halos is rather insensitive to other cosmological parameters, it can in principle be an independent discriminator of modified gravity. We speculate a possibility of using the relative abundance of low surface brightness galaxies (LSBGs) as a test of general relativity given that the formation of the LSBGs occurs in fast spinning dark halos.

  11. HIDE AND SEEK BETWEEN ANDROMEDA'S HALO, DISK, AND GIANT STREAM

    SciTech Connect

    Clementini, Gisella; Contreras Ramos, Rodrigo; Federici, Luciana; Macario, Giulia; Tosi, Monica; Bellazzini, Michele; Fusi Pecci, Flavio; Diolaiti, Emiliano; Cacciari, Carla; Beccari, Giacomo; Testa, Vincenzo; Giallongo, Emanuele; Di Paola, Andrea; Gallozzi, Stefano; Cignoni, Michele; Marano, Bruno; Marconi, Marcella; Ripepi, Vincenzo; Ragazzoni, Roberto; Smareglia, Riccardo

    2011-12-10

    Photometry in B, V (down to V {approx} 26 mag) is presented for two 23' Multiplication-Sign 23' fields of the Andromeda galaxy (M31) that were observed with the blue channel camera of the Large Binocular Telescope during the Science Demonstration Time. Each field covers an area of about 5.1 Multiplication-Sign 5.1 kpc{sup 2} at the distance of M31 ({mu}{sub M31} {approx} 24.4 mag), sampling, respectively, a northeast region close to the M31 giant stream (field S2) and an eastern portion of the halo in the direction of the galaxy minor axis (field H1). The stream field spans a region that includes Andromeda's disk and giant stream, and this is reflected in the complexity of the color-magnitude diagram of the field. One corner of the halo field also includes a portion of the giant stream. Even though these demonstration time data were obtained under non-optimal observing conditions, the B photometry, which was acquired in time-series mode, allowed us to identify 274 variable stars (among which 96 are bona fide and 31 are candidate RR Lyrae stars, 71 are Cepheids, and 16 are binary systems) by applying the image subtraction technique to the selected portions of the observed fields. Differential flux light curves were obtained for the vast majority of these variables. Our sample mainly includes pulsating stars that populate the instability strip from the Classical Cepheids down to the RR Lyrae stars, thus tracing the different stellar generations in these regions of M31 down to the horizontal branch of the oldest (t {approx} 10 Gyr) component.

  12. On the reversal of star formation rate-density relation at z = 1: Insights from simulations

    SciTech Connect

    Tonnesen, Stephanie; Cen, Renyue E-mail: cen@astro.princeton.edu

    2014-06-20

    Recent surveys have found a reversal of the star formation rate (SFR)-density relation at z = 1 from that at z = 0, while the sign of the slope of the color-density relation remains unchanged. We use adaptive mesh refinement cosmological hydrodynamic simulations of a 21 × 24 × 20 h {sup –3} Mpc{sup 3} region to examine the SFR-density and color-density relations of galaxies at z = 0 and z = 1. The local environmental density is defined by the dark matter mass in spheres of radius 1 h {sup –1} Mpc, and we probe two decades of environmental densities. Our simulations produce a large increase of SFR with density at z = 1, as in the Elbaz et al. observations. We also find a significant evolution to z = 0, where the SFR-density relation is much flatter. The simulated color-density relation is consistent from z = 1 to z = 0, in agreement with observations. We find that the increase in SFR with local density at z = 1 is due to a growing population of star-forming galaxies in higher-density environments. At z = 0 and z = 1 both the SFR and cold gas mass are correlated with the galaxy halo mass, and therefore the correlation between median halo mass and local density is an important cause of the SFR-density relation at both redshifts. However, at z = 0 the local density on 1 h {sup –1} Mpc scales affects galaxy SFRs as much as halo mass. Finally, we find indications that while at z = 0 high-density environments depress galaxy SFRs, at z = 1 high-density environments tend to increase SFRs.

  13. The Splashback Radius as a Physical Halo Boundary and the Growth of Halo Mass

    NASA Astrophysics Data System (ADS)

    More, Surhud; Diemer, Benedikt; Kravtsov, Andrey V.

    2015-09-01

    The boundaries of cold dark matter halos are commonly defined to enclose a density contrast Δ relative to a reference (mean or critical) density. We argue that a more physical halo boundary choice is the radius at which accreted matter reaches its first orbital apocenter after turnaround. This splashback radius, {R}{sp}, manifests itself as a sharp density drop in the halo outskirts, at a location that depends upon the mass accretion rate. We present calibrations of {R}{sp} and the enclosed mass, {M}{sp}, as a function of mass accretion rate and peak height. We find that {R}{sp} is in the range ≈ 0.8-1{R}200{{m}} for rapidly accreting halos and is ≈ 1.5{R}200{{m}} for slowly accreting halos. Thus, halos and their environmental effects can extend well beyond the conventionally defined “virial” radius. We show that {M}{sp} and {R}{sp} evolve relatively strongly compared to other commonly used definitions. In particular, {M}{sp} evolves significantly even for the smallest dwarf-sized halos at z = 0. We also contrast {M}{sp} with the mass enclosed within four scale radii of the halo density profile, {M}\\lt 4{r{{s}}}, which characterizes the inner halo. During the early stages of halo assembly, {M}{sp} and {M}\\lt 4{r{{s}}} evolve similarly, but in the late stages {M}\\lt 4{r{{s}}} stops increasing while {M}{sp} continues to grow significantly. This illustrates that halos at low z can have “quiet” interiors while continuing to accrete mass in their outskirts. We discuss potential observational estimates of the splashback radius and show that it may already have been detected in galaxy clusters.

  14. Halo occupation numbers and galaxy bias

    NASA Astrophysics Data System (ADS)

    Peacock, J. A.; Smith, R. E.

    2000-11-01

    We propose a heuristic model that displays the main features of realistic theories for galaxy bias. We first show that the low-order clustering statistics of the dark-matter distribution depend almost entirely on the locations and density profiles of dark-matter haloes. The quasi-linear mass correlations are in fact reproduced well by a model of independent randomly-placed haloes. The distribution of galaxies within the halo density field depends on: (i) the efficiency of galaxy formation, as manifested by the halo occupation number - the number of galaxies brighter than some sample limit contained in a halo of a given mass; (ii) the location of these galaxies within their halo. The first factor is constrained by the empirical luminosity function of groups. For the second factor, we assume that one galaxy marks the halo centre, with any remaining galaxies acting as satellites that trace the halo mass. This second assumption is essential if small-scale galaxy correlations are to remain close to a single power law, rather than flattening in the same way as the correlations of the overall density field. These simple assumptions amount to a recipe for non-local bias, in which the probability of finding a galaxy is not a simple function of its local mass density. We have applied this prescription to some CDM models of current interest, and find that the predictions are close to the observed galaxy correlations for a flat Ω=0.3 model (ΛCDM), but not for an Ω=1 model with the same power spectrum (τCDM). This is an inevitable consequence of cluster normalization for the power spectra: cluster-scale haloes of given mass have smaller core radii for high Ω, and hence display enhanced small-scale clustering. Finally, the pairwise velocity dispersion of galaxies in the ΛCDM model is lower than that of the mass, allowing cluster-normalized models to yield a realistic Mach number for the peculiar velocity field. This is largely due to the strong variation of galaxy

  15. HaloSat- A CubeSat to Study the Hot Galactic Halo

    NASA Astrophysics Data System (ADS)

    Kaaret, Philip

    We propose to develop, build, and fly HaloSat, a CubeSat capable of measuring the oxygen line emission from the hot Galactic halo. A dedicated CubeSat enables an instrument design and observing strategy to maximize the halo signal while minimizing foregrounds from solar wind charge exchange interactions within the solar system. We will use HaloSat to map the distribution of hot gas in the Milky Way and determine whether it fills an extended, and thus massive halo, or whether the halo is compact, and thus does not contribute significantly to the total mass of the Milky Way. HaloSat can be accomplished at modest cost using a CubeSat, a novel platform for space astrophysics missions. We will use a commercially available CubeSat bus and commercially available X-ray detectors to reduce development risk and minimize overall mission cost. HaloSat builds on the initiatives of GSFC/Wallops Flight Facility (WFF) in the development of CubeSats for low cost access to space and relies on the technical expertise of WFF personnel for spacecraft and mission design and operations. The team, from University of Iowa (UI), GSFC, Johns Hopkins, and CNRS (France), contains experts in X-ray detector development and data analysis and the astrophysics of hot plasmas and Galactic structure. The UI team will include a number of junior researchers (undergraduates, graduate students, and a postdoc) and help train them for future leadership roles on NASA space flight missions.

  16. Simulating Halos with the Caterpillar Project

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2016-04-01

    The Caterpillar Project is a beautiful series of high-resolution cosmological simulations. The goal of this project is to examine the evolution of dark-matter halos like the Milky Ways, to learn about how galaxies like ours formed. This immense computational project is still in progress, but the Caterpillar team is already providing a look at some of its first results.Lessons from Dark-Matter HalosWhy simulate the dark-matter halos of galaxies? Observationally, the formation history of our galaxy is encoded in galactic fossil record clues, like the tidal debris from disrupted satellite galaxies in the outer reaches of our galaxy, or chemical abundance patterns throughout our galactic disk and stellar halo.But to interpret this information in a way that lets us learn about our galaxys history, we need to first test galaxy formation and evolution scenarios via cosmological simulations. Then we can compare the end result of these simulations to what we observe today.This figure illustrates the difference that mass resolution makes. In the left panel, the mass resolution is 1.5*10^7 solar masses per particle. In the right panel, the mass resolution is 3*10^4 solar masses per particle [Griffen et al. 2016]A Computational ChallengeDue to how computationally expensive such simulations are, previous N-body simulations of the growth of Milky-Way-like halos have consisted of only one or a few halos each. But in order to establish a statistical understanding of how galaxy halos form and find out whether the Milky Ways halo is typical or unusual! it is necessary to simulate a larger number of halos.In addition, in order to accurately follow the formation and evolution of substructure within the dark-matter halos, these simulations must be able to resolve the smallest dwarf galaxies, which are around a million solar masses. This requires an extremely high mass resolution, which adds to the computational expense of the simulation.First OutcomesThese are the challenges faced by

  17. GRAVITATIONALLY CONSISTENT HALO CATALOGS AND MERGER TREES FOR PRECISION COSMOLOGY

    SciTech Connect

    Behroozi, Peter S.; Wechsler, Risa H.; Wu, Hao-Yi; Busha, Michael T.; Klypin, Anatoly A.; Primack, Joel R. E-mail: rwechsler@stanford.edu

    2013-01-20

    We present a new algorithm for generating merger trees and halo catalogs which explicitly ensures consistency of halo properties (mass, position, and velocity) across time steps. Our algorithm has demonstrated the ability to improve both the completeness (through detecting and inserting otherwise missing halos) and purity (through detecting and removing spurious objects) of both merger trees and halo catalogs. In addition, our method is able to robustly measure the self-consistency of halo finders; it is the first to directly measure the uncertainties in halo positions, halo velocities, and the halo mass function for a given halo finder based on consistency between snapshots in cosmological simulations. We use this algorithm to generate merger trees for two large simulations (Bolshoi and Consuelo) and evaluate two halo finders (ROCKSTAR and BDM). We find that both the ROCKSTAR and BDM halo finders track halos extremely well; in both, the number of halos which do not have physically consistent progenitors is at the 1%-2% level across all halo masses. Our code is publicly available at http://code.google.com/p/consistent-trees. Our trees and catalogs are publicly available at http://hipacc.ucsc.edu/Bolshoi/.

  18. Sign language and autism.

    PubMed

    Bonvillian, J D; Nelson, K E; Rhyne, J M

    1981-03-01

    Research findings and issues in teaching sign language to nonspeaking autistic children are reviewed. Data on over 100 children indicate that nearly all autistic children learn receptive and expressive signs, and many learn to combine signs. These children also exhibit marked improvement in adaptive behaviors. Speech skills are acquired by fewer children and may be developed through simultaneous speech and sign training. Possible explanations for these results are given, together with suggestions for future research and data collection. Recommended innovations include exposure to fluent signers and training in discourse and code-switching. Different sign language teaching methods need to be investigated more fully, including emphasis on training sign language within the children's total environment and with greater staff and parental participation.

  19. Halo Spin Parameter in Cosmological Simulations

    NASA Astrophysics Data System (ADS)

    Ahn, Jieun; Kim, Juhan; Shin, Jihye; Kim, Sungsoo S.; Choi, Yun-Young

    2014-04-01

    Using a cosmological ΛCDM simulation, we analyze the differences between the widely-used spin parameters suggested by Peebles and Bullock. The dimensionless spin parameter λ proposed by Peebles is theoretically well-justified but includes an annoying term, the potential energy, which cannot be directly obtained from observations and is computationally expensive to calculate in numerical simulations. The Bullock's spin parameter λ^' avoids this problem assuming the isothermal density profile of a virialized halo in the Newtonian potential model. However, we find that there exists a substantial discrepancy between λ and λ^' depending on the adopted potential model (Newtonian or Plummer) to calculate the halo total energy and that their redshift evolutions differ to each other significantly. Therefore, we introduce a new spin parameter, λ^{''}, which is simply designed to roughly recover the value of λ but to use the same halo quantities as used in λ^'. If the Plummer potential is adopted, the λ^{''} is related to the Bullock's definition as λ^{''} = 0.80× (1 + z)^{-1/12} λ^'. Hence, the new spin parameter λ^{''} distribution becomes consistent with a log-normal distribution frequently seen for the λ^' while its mean value is much closer to that of λ. On the other hand, in case of the Newtonian potential model, we obtain the relation of λ^{''}=(1+z)^{-1/8}λ^{'}; there is no significant difference at z = 0 as found by others but λ^{'} becomes more overestimated than λ or λ^{''} at higher redshifts. We also investigate the dependence of halo spin parameters on halo mass and redshift. We clearly show that although the λ^' for small-mass halos with M_h < 2× 10^{12} M_odot seems redshift independent after z=1, all the spin parameters explored, on the whole, show a stronger correlation with the increasing halo mass at higher redshifts.

  20. Dark Matter Properties and Halo Central Densities

    NASA Astrophysics Data System (ADS)

    Alam, S. M. Khairul; Bullock, James S.; Weinberg, David H.

    2002-06-01

    Using an analytic model calibrated against numerical simulations, we calculate the central densities of dark matter halos in a ``conventional'' cold dark matter model with a cosmological constant (LCDM) and in a ``tilted'' model (TLCDM) with slightly modified parameters motivated by recent analyses of Lyα forest data. We also calculate how warm dark matter (WDM) would modify these predicted densities by delaying halo formation and imposing phase-space constraints. As a measure of central density, we adopt the quantity ΔV/2, the density within the radius RV/2 at which the halo rotation curve falls to half of its maximum value, in units of the critical density. We compare the theoretical predictions to values of ΔV/2 estimated from the rotation curves of dark matter-dominated disk galaxies. Assuming that dark halos are described by Navarro-Frenk-White profiles, our results suggest that the conventional LCDM model predicts excessively high dark matter densities, unless there is some selection bias in the data toward the low-concentration tail of the halo distribution. A WDM model with particle mass 0.5-1 keV provides a better match to the observational data. However, the modified cold dark matter model, TLCDM, fits the data equally well, suggesting that the solution to the ``halo cores'' problem might lie in moderate changes to cosmological parameters rather than radical changes to the properties of dark matter. If cold dark matter halos have the steeper density profiles found by Moore et al., then neither conventional LCDM nor TLCDM can reproduce the observed central densities.

  1. The Milky Way, the Galactic Halo, and the Halos of Galaxies

    NASA Astrophysics Data System (ADS)

    Gerhard, Ortwin

    2016-08-01

    The Milky Way, ``our'' Galaxy, is currently the subject of intense study with many ground-based surveys, in anticipation of upcoming results from the Gaia mission. From this work we have been learning about the full three-dimensional structure of the Galactic box/peanut bulge, the distribution of stars in the bar and disk, and the many streams and substructures in the Galactic halo. The data indicate that a large fraction of the Galactic halo has been accreted from outside. Similarly, in many external galaxy halos there is now evidence for tidal streams and accretion of satellites. To study these features requires exquisite, deep photometry and spectroscopy. These observations illustrate how galaxy halos are still growing, and sometimes can be used to ``time'' the accretion events. In comparison with cosmological simulations, the structure of galaxy halos gives us a vivid illustration of the hierarchical nature of our Universe.

  2. HaloSat - A CubeSat to Study the Hot Galactic Halo

    NASA Astrophysics Data System (ADS)

    Kaaret, Philip

    2017-01-01

    Observations of the nearby universe fail to locate about half of the baryons observed in the early universe. The missing baryons may be in hot galactic halos. HaloSat is a CubeSat designed to map oxygen line emission (O VII and O VIII) around the Milky Way in order to constrain the mass and spatial distribution of hot gas in the halo. HaloSat has a grasp competitive with current X-ray observatories. Its observing program will be optimized to minimize contributions from solar wind charge exchange (SWCX) emission that limit the accuracy of current measurements. We will describe the HaloSat mission concept, progress towards its implementation, and plans for archiving and distribution of the data.

  3. HaloSat - A CubeSat to Study the Hot Galactic Halo

    NASA Astrophysics Data System (ADS)

    Kaaret, Philip

    2016-04-01

    Observations of the nearby universe fail to locate about half of the normal matter (baryons) observed in the early universe. The missing baryons may be in hot galactic halos. HaloSat is a CubeSat designed to map oxygen line emission (O VII and O VIII) around the Milky Way in order to constrain the mass and spatial distribution of hot gas in the halo. HaloSat has a grasp competitive with current X-ray observatories. Its observing program will be optimized to minimize contributions from solar wind charge exchange (SWCX) emission that limit the accuracy of current measurements. We will describe the HaloSat mission concept, progress towards its implementation, and plans for archiving and distribution of the data.

  4. Electric Properties of One-Neutron Halo Nuclei in Halo EFT

    NASA Astrophysics Data System (ADS)

    Braun, Jonas; Hammer, Hans-Werner

    2017-03-01

    We exploit the separation of scales in weakly-bound nuclei to compute E2 transitions and electric form factors in a halo effective field theory (EFT) framework. The relevant degrees of freedom are the core and the halo neutron. The EFT expansion is carried out in powers of R_{core}/R_{halo}, where R_{core} and R_{halo} denote the length scales of the core and halo, respectively. We include the strong s-wave and d-wave interactions by introducing dimer fields. The dimer propagators are regulated by employing the power divergence subtraction scheme and matched to the effective range expansion in the respective channel. Electromagnetic interactions are included via minimal substitution in the Lagrangian. We demonstrate that, depending on the observable and respective partial wave, additional local gauge-invariant operators contribute in LO, NLO and higher orders.

  5. Military Vital Sign Monitor.

    DTIC Science & Technology

    1984-09-30

    agreement, however, are of a nonspecific nature, and neither discuss vital sign monitors or other technology based life support equipment, nor...evacuations. STANAG 2126, "Medical First-Aid Equipment and Supplies," does not discuss vital sign monitors or other life support equipment. No...1 safety of any life support equipment and ,therefore, do not affect vital sign monitors selected as a result of this investigation. However, they do

  6. Food Signs in Radiology

    PubMed Central

    Hussain, Mehboob; Al Damegh, Saleh

    2007-01-01

    Objective: Certain diseases show classic radiological signs that resemble various types of food items like fruits, meat, vegetables, eggs, bakery, grocery and confectionary items. In this article various food signs are discussed and correlated with the various food items in a pictorial way. The objective of this pictorial essay is to provide the information and learn the characteristic radiological signs resembling various food items. These food signs are easy to recognize and allows a confident diagnosis on the basis of imaging findings alone or can narrow down the differential diagnosis. PMID:21475464

  7. Statistical Aspects of X-Class Halo and Non-Halo Events, 1996-2014

    NASA Technical Reports Server (NTRS)

    Wilson, Robert M.

    2016-01-01

    Of the 166 X-class events that occurred during the interval 1996-2014, 80 had associations with halo events, 68 had no associations with halo events, and 18 occurred during LASCO (Large Angle and Spectrometric COronagraph) data gaps. Both the duration and location of the X-class halo events proved to be statistically important parameters with respect to the geo-effectiveness of the events. Forty-four of the 80 X-class halo events occurred within 45 degrees of the Sun's central meridian and 47 of the 80 had duration greater than or equal to 30 minutes, whereas only 28 of the 68 X-class non-halo events occurred within 45 degrees of the Sun's central meridian (2 events have unknown location) and 22 of the 68 had duration greater than or equal to 30 minutes. Ignoring the 4 largest X-class flares greater than or equal to X4.0 during the LASCO data gaps, 17 of the remaining 20 were associated with halo events, and 14 of the 17 had at least one geo-magnetically disturbed day (Ap (i.e. NOAA's Ap* (ApStar)index: the major magnetic storms going back to 1932) greater than or equal to 25 nanotesias) within 1-5 days following the X-class halo event. Based on the hourly Dst (Disturbance storm time) index, the most geo-effective X-class halo event during the interval 1996-2014 was that of an X1.7 flare that occurred on 2001 March 29 at 0957, having an hourly Disturbance storm time minimum equal to minus 387 nanotesias. On average, the X-class halo events (80 events) were found to have a mean duration (42 minutes) slightly longer than the mean duration (29 minutes) of the X-class non-halo events (68 events) with the difference in the means being statistically important at the 1 percent level of significance.

  8. Separation of Peptides on HALO 2-Micron Particles.

    PubMed

    Mant, Colin T; Hodges, Robert S

    2016-08-01

    Reversed-phase high-performance liquid chromatography (RP-HPLC) is of fundamental importance to the isolation and separation of peptides, proteins, and other biomolecules. Hence, there is a continuing high demand for the development of RP-HPLC stationary-phase materials with enhanced separation efficiency. HALO packing materials began the revolution in "core-shell" technology with the advantages of faster separations, higher resolution and peak capacity, high temperature stability, and rugged reliable performance compared to traditional HPLC and UHPLC. These materials are characterized by a solid core surrounded by a thin layer of porous material, and represent a technology for the future with continuing refinements. Such refinements are aided via the use of designed synthetic peptide standards during stationary-phase development. Concomitantly, such standards also enable the researcher to monitor RP-HPLC column performance and develop optimized separation protocols for peptides from a wide array of sources. © 2016 by John Wiley & Sons, Inc.

  9. Sign reversal of junction magnetoresistance in p-La0.7Ca0.3MnO3/SiO2/n-Si heterostructure: a possibility in spintronics application.

    PubMed

    Giri, S K; Nath, T K

    2012-10-01

    We have fabricated a p-La0.7Ca0.3MnO3/SiO2/n-Si heterostructure, consisting of a p-type manganite (La0.7Ca0.3MnO3) and n-type Si with a interfacial layer of SiO2 with typical thickness of about 9 nm using pulsed laser deposition technique. The junction exhibits rectifying behavior over the temperature range of 10-300 K with rectification factor 52 at room temperature. Investigation on the electrical properties of p-La0.7Ca0.3MnO3/SiO2/n-Si heterostructure exhibits nonlinear J-V characteristics in a wide temperature range. A crossover from negative to positive junction magnetoresistance (JMR) is observed in p-La0.7Ca0.3MnO3/SiO2/n-Si heterostructure in current perpendicular to film plane (CPP) geometry. The temperature dependent sign of junction magnetoresistance of the heterojunction has been investigated carefully in details. It is found that the junction exhibits the positive junction magnetoresistance when the temperature is greater than the ferromagnetic to paramagnetic transition temperature (Tc) of the top highly spin-polarized half-metallic ferromagnetic La0.7Ca0.3MnO3 manganite film layer. The relation between junction magnetoresistance and external magnetic field is found to be of (delta rho/rho approximately equal alphaHbeta) type having both alpha and beta temperature dependent. We attribute the emergence of negative JMR at lower temperature (< Tc) and positive JMR at higher temperature (> Tc) to the quantum mechanical tunneling transport mechanism across the heterojunction. Our results might be very useful to fabricate artificial devices using the manganite-based heterojunction grown on single crystalline n-Si (100) in spintronics device applications.

  10. Sun-Earth L1 Region Halo-To-Halo Orbit and Halo-To-LisaJous Orbit Transfers

    NASA Technical Reports Server (NTRS)

    Roberts, Craig E.; DeFazio, Robert

    2004-01-01

    Practical techniques for designing transfer trajectories between Libration Point Orbits (LPOs) are presented. Motivation for development of these techniques was provided by a hardware contingency experienced by the Solar Heliospheric Observatory (SOHO), a joint mission of the European Space Agency (ESA) and the National Aeronautics and Space Administration (NASA) orbiting the L1 point of the Sun-Earth system. A potential solution to the problem involved a transfer from SOHO s periodic halo orbit to a new LPO of substantially different dimensions. Assuming the SOHO halo orbit as the departure orbit, several practical LPO transfer techniques were developed to obtain new Lissajous or periodic halo orbits that satisfy mission requirements and constraints. While not implemented for the SOHO mission, practical LPO transfer techniques were devised that are generally applicable to current and future LPO missions.

  11. Why are halo coronal mass ejections faster?

    NASA Astrophysics Data System (ADS)

    Zhang, Qing-Min; Guo, Yang; Chen, Peng-Fei; Ding, Ming-De; Fang, Cheng

    2010-05-01

    Halo coronal mass ejections (CMEs) have been to be significantly faster than normal CMEs, which is a long-standing puzzle. In order to solve the puzzle, we first investigate the observed properties of 31 limb CMEs that clearly display loop-shaped frontal loops. The observational results show a strong tendency that slower CMEs are weaker in white-light intensity. Then, we perform a Monte Carlo simulation of 20000 artificial limb CMEs that have an average velocity of ~523 km s-1. The Thomson scattering of these events is calculated when they are assumed to be observed as limb and halo events, respectively. It is found that the white-light intensity of many slow CMEs becomes remarkably reduced when they turn from being viewed as a limb event to being viewed as a halo event. When the intensity is below the background solar wind fluctuation, it is assumed that they would be missed by coronagraphs. The average velocity of “detectable" halo CMEs is ~922 km s-1 very close to the observed value. This also indicates that wider events are more likely to be recorded. The results soundly suggest that the higher average velocity of halo CMEs is due to that a majority of slow events and some of narrow fast events carrying less material are so faint that they are blended with the solar wind fluctuations, and therefore are not observed.

  12. The angular momentum distribution in galactic halos

    NASA Astrophysics Data System (ADS)

    Quinn, P. J.; Zurek, W. H.

    1988-08-01

    N-body simulations are used to model the formation of individual galactic halos from scale-free density perturbations in universes dominated by cold, nondissipative dark matter. In well-mixed halos, the angular momentum distribution is shown to have a systematic behavior with power law index n corresponding to that found for circular rotation curves. For a given n, the distribution of angular momentum has the same trend with radius and energy as that implied for a halo in which all the matter has its maximum possible angular momentum. Dynamical mixing during the relaxation of the halo redistributes both angular momentum and binding energy in an orderly manner. The organized nature of the collapse means that relaxation is not completely violent and that the secondary infall paradigm, in its simplest form, needs to be modified to include the organizing effects of dynamical friction. It is shown that the Mestel hypothesis is not consistent with the final collapsed state of halos, but may be applicable to the collapse of the disks of spirals.

  13. A UNIVERSAL MODEL FOR HALO CONCENTRATIONS

    SciTech Connect

    Diemer, Benedikt; Kravtsov, Andrey V.

    2015-01-20

    We present a numerical study of dark matter halo concentrations in ΛCDM and self-similar cosmologies. We show that the relation between concentration, c, and peak height, ν, exhibits the smallest deviations from universality if halo masses are defined with respect to the critical density of the universe. These deviations can be explained by the residual dependence of concentration on the local slope of the matter power spectrum, n, which affects both the normalization and shape of the c-ν relation. In particular, there is no well-defined floor in the concentration values. Instead, the minimum concentration depends on redshift: at fixed ν, halos at higher z experience steeper slopes n, and thus have lower minimum concentrations. We show that the concentrations in our simulations can be accurately described by a universal seven-parameter function of only ν and n. This model matches our ΛCDM results to ≲ 5% accuracy up to z = 6, and matches scale-free Ω{sub m} = 1 models to ≲ 15%. The model also reproduces the low concentration values of Earth-mass halos at z ≈ 30, and thus correctly extrapolates over 16 orders of magnitude in halo mass. The predictions of our model differ significantly from all models previously proposed in the literature at high masses and redshifts. Our model is in excellent agreement with recent lensing measurements of cluster concentrations.

  14. Static galactic halo and galactic wind

    NASA Technical Reports Server (NTRS)

    Ko, Chung-Ming

    1993-01-01

    Although the exact state of the interstellar medium (ISM) in our Galaxy (other galaxies as well) is not clear at all, the 'common consensus' is that a rough pressure balance (or equipartition of energy) exists between different components and phases: cold, warm, hot phases of the ISM, magnetic field, cosmic rays, etc. If the halo of a galaxy is taken to be an extension of the ISM, then its structure is influenced by various ISM components. A 'complete' description of the halo is evidently very complicated. This paper gives a brief account on cosmic ray halo, which emphasizes the role played by cosmic rays. The interaction between cosmic rays and thermal plasma is facilitated by magnetic field. The cosmic rays are scattered by hydromagnetic waves (e.g., Alfven waves) which in turn can be generated by cosmic ray streaming instability. This constitutes a self-consistent picture. Since we are interested in the structure of the halo, we adopted a hydrodynamic model in which the cosmic rays and waves are described by their pressures. In general there are two classes of halos: static and dynamic.

  15. A "Light," Centrally Concentrated Milky Way Halo?

    NASA Astrophysics Data System (ADS)

    Rashkov, Valery; Pillepich, Annalisa; Deason, Alis J.; Madau, Piero; Rockosi, Constance M.; Guedes, Javiera; Mayer, Lucio

    2013-08-01

    We discuss a novel approach to "weighing" the Milky Way (MW) dark matter halo, one that combines the latest samples of halo stars selected from the Sloan Digital Sky Survey (SDSS) with state of the art numerical simulations of MW analogs. The fully cosmological runs employed in the present study include "Eris," one of the highest resolution hydrodynamical simulations of the formation of a M vir = 8 × 1011 M ⊙ late-type spiral, and the dark-matter-only M vir = 1.7 × 1012 M ⊙ "Via Lactea II" (VLII) simulation. Eris provides an excellent laboratory for creating mock SDSS samples of tracer halo stars, and we successfully compare their density, velocity anisotropy, and radial velocity dispersion profiles with the observational data. Most mock SDSS realizations show the same "cold veil" recently observed in the distant stellar halo of the MW, with tracers as cold as σlos ≈ 50 km s-1 between 100 and 150 kpc. Controlled experiments based on the integration of the spherical Jeans equation as well as a particle tagging technique applied to VLII show that a "heavy" M vir ≈ 2 × 1012 M ⊙ realistic host produces a poor fit to the kinematic SDSS data. We argue that these results offer added evidence for a "light," centrally concentrated MW halo.

  16. A Universal Model for Halo Concentrations

    NASA Astrophysics Data System (ADS)

    Diemer, Benedikt; Kravtsov, Andrey V.

    2015-01-01

    We present a numerical study of dark matter halo concentrations in ΛCDM and self-similar cosmologies. We show that the relation between concentration, c, and peak height, ν, exhibits the smallest deviations from universality if halo masses are defined with respect to the critical density of the universe. These deviations can be explained by the residual dependence of concentration on the local slope of the matter power spectrum, n, which affects both the normalization and shape of the c-ν relation. In particular, there is no well-defined floor in the concentration values. Instead, the minimum concentration depends on redshift: at fixed ν, halos at higher z experience steeper slopes n, and thus have lower minimum concentrations. We show that the concentrations in our simulations can be accurately described by a universal seven-parameter function of only ν and n. This model matches our ΛCDM results to <~ 5% accuracy up to z = 6, and matches scale-free Ωm = 1 models to <~ 15%. The model also reproduces the low concentration values of Earth-mass halos at z ≈ 30, and thus correctly extrapolates over 16 orders of magnitude in halo mass. The predictions of our model differ significantly from all models previously proposed in the literature at high masses and redshifts. Our model is in excellent agreement with recent lensing measurements of cluster concentrations.

  17. Globular Cluster Contributions to the Galactic Halo

    NASA Astrophysics Data System (ADS)

    Martell, Sarah; Grebel, Eva; Lai, David

    2010-08-01

    The goal of this project is to confirm chemically that globular clusters are the source of as much as half the population of the Galactic halo. Using moderate-resolution spectroscopy from the SEGUE survey, we have identified a previously unknown population of halo field giants with distinctly strong CN features. CN variations are typically only observed in globular clusters, so these stars are interpreted as immigrants to the halo that originally formed in globular clusters. In one night of Keck/HIRES time, we will obtain high-quality, high- resolution spectra for five such stars, and determine abundances of O, Na, Mg, Al, alpha, iron-peak and neutron-capture elements. With this information we can state clearly whether these unusual CN-strong halo stars carry the full abundance pattern seen in CN-strong globular cluster stars, with depleted C, O, and Mg and enhanced N, Na, and Al. This type of coarse ``chemical tagging'' will allow a clearer division of the Galactic halo into contributions from globular clusters and from dwarf galaxies, and will place constraints on theoretical models of globular cluster formation and evolution.

  18. Information Status and Word Order in Croatian Sign Language

    ERIC Educational Resources Information Center

    Milkovic, Marina; Bradaric-Joncic, Sandra; Wilbur, Ronnie B.

    2007-01-01

    This paper presents the results of research on information structure and word order in narrative sentences taken from signed short stories in Croatian Sign Language (HZJ). The basic word order in HZJ is SVO. Factors that result in other word orders include: reversible arguments, verb categories, locative constructions, contrastive focus, and prior…

  19. The settling of warped disks in oblate dark halos

    NASA Technical Reports Server (NTRS)

    Dubinski, John; Kuijken, Konrad

    1995-01-01

    When a galaxy forms, the disk may initially be tilted with respect to a flattened dark halo. The misalignment between the disk and the halo is a common explanation for galactic disk warps, since in this state disks have precessing bending modes which resemble real warps. The gravitational response of the halo has often been ignored, and its strength and effect on possible bending modes is unknown. We therefore calculate the response of an oblate halo to a precessing inclined exponential disk using a variety of techniques. We construct models with a rigid exponential disk precessing in a particle halo, a particle disk precessing inside a static bulge/halo potential, and a self-consistent model with a particle disk, bulge, and halo. When the disk: halo mass ratio is small (approximately 10%) within 5 exponential scale radii, the disk settles to the equatorial plane of the halo within five orbital times. When the disk and halo mass are comparable, the halo rapidly aligns with the disk within a few orbital times, while the disk inclination drops. The rapid response of the halo to an inclined precessing disk suggests that the warps seen in galactic disks are not due to a misalignment between the disk and the inner halo. If a galaxy forms inclined to the principal plane of a dark halo, either the disk will settle to a pricipal plane or the inner halo will twist to align with the disk. The outer halo will remain misaligned for a much longer time and therefore may still exert a torque. Warped bending modes may still exist if the misalignment of the outer halo persists for a Hubble time.

  20. The settling of warped disks in oblate dark halos

    NASA Technical Reports Server (NTRS)

    Dubinski, John; Kuijken, Konrad

    1995-01-01

    When a galaxy forms, the disk may initially be tilted with respect to a flattened dark halo. The misalignment between the disk and the halo is a common explanation for galactic disk warps, since in this state disks have precessing bending modes which resemble real warps. The gravitational response of the halo has often been ignored, and its strength and effect on possible bending modes is unknown. We therefore calculate the response of an oblate halo to a precessing inclined exponential disk using a variety of techniques. We construct models with a rigid exponential disk precessing in a particle halo, a particle disk precessing inside a static bulge/halo potential, and a self-consistent model with a particle disk, bulge, and halo. When the disk: halo mass ratio is small (approximately 10%) within 5 exponential scale radii, the disk settles to the equatorial plane of the halo within five orbital times. When the disk and halo mass are comparable, the halo rapidly aligns with the disk within a few orbital times, while the disk inclination drops. The rapid response of the halo to an inclined precessing disk suggests that the warps seen in galactic disks are not due to a misalignment between the disk and the inner halo. If a galaxy forms inclined to the principal plane of a dark halo, either the disk will settle to a pricipal plane or the inner halo will twist to align with the disk. The outer halo will remain misaligned for a much longer time and therefore may still exert a torque. Warped bending modes may still exist if the misalignment of the outer halo persists for a Hubble time.

  1. Standardization of Sign Languages

    ERIC Educational Resources Information Center

    Adam, Robert

    2015-01-01

    Over the years attempts have been made to standardize sign languages. This form of language planning has been tackled by a variety of agents, most notably teachers of Deaf students, social workers, government agencies, and occasionally groups of Deaf people themselves. Their efforts have most often involved the development of sign language books…

  2. Standardization of Sign Languages

    ERIC Educational Resources Information Center

    Adam, Robert

    2015-01-01

    Over the years attempts have been made to standardize sign languages. This form of language planning has been tackled by a variety of agents, most notably teachers of Deaf students, social workers, government agencies, and occasionally groups of Deaf people themselves. Their efforts have most often involved the development of sign language books…

  3. UCR Library Sign System Manual.

    ERIC Educational Resources Information Center

    California Univ., Riverside. Library.

    This manual outlines the procedures to be used for producing and placing signs within the libraries of the University of California, Riverside and presents examples of signs which conform to the library sign policy. The sign policy itself is described as well as procedures for requesting new or revised signs and for sign removal. Drawings of…

  4. Stability of BEC galactic dark matter halos

    NASA Astrophysics Data System (ADS)

    Guzmán, F. S.; Lora-Clavijo, F. D.; González-Avilés, J. J.; Rivera-Paleo, F. J.

    2013-09-01

    In this paper we show that spherically symmetric BEC dark matter halos, with the sin r/r density profile, that accurately fit galactic rotation curves and represent a potential solution to the cusp-core problem are unstable. We do this by introducing back the density profiles into the fully time-dependent Gross-Pitaevskii-Poisson system of equations. Using numerical methods to track the evolution of the system, we found that these galactic halos lose mass at an approximate rate of half of its mass in a time scale of dozens of Myr. We consider this time scale is enough as to consider these halos are unstable and unlikely to be formed. We provide some arguments to show that this behavior is general and discuss some other drawbacks of the model that restrict its viability.

  5. Systematic Problems With Stellar Halo Modelling

    NASA Astrophysics Data System (ADS)

    Bailin, Jeremy

    2012-05-01

    Stellar halos contain a small fraction of the stellar mass of a galaxy. The dynamic range required to model the substructure within this small component while simultaneously modeling the main galaxy is currently unobtainable, which has lead to the prevalence of stellar halo models that tag stellar content onto dark matter particles in pure dark matter simulations, making it computationally feasible (e.g. Bullock & Johnston 2005; Cooper et al. 2010). Using paired simulations with identical initial conditions, we estimate the magnitude of the systematic effects these simplifications have on the structure of the halos. We find that (1) "painting" and (2) neglecting baryonic processes each introduce factor-of-several changes to the amount of substructure predicted. We therefore urge caution when interpreting differences between models and observations that are at this level.

  6. The Implication of MOND for Dark Haloes

    NASA Astrophysics Data System (ADS)

    Huang, Yi-Cheng; Kosowsky, A.

    2006-12-01

    It is always interesting that how much implication that Milgrom's relation could provide, even phenomenologically. With just one assumption that the gravitational acceleration goes like 1/r instead of Newton's law, 1/r2, when the acceleration is smaller than the value $10-10m/sec2, it is well known that MOND can give a better description of the rotational curves in spiral galaxies. In this research, we explore the configuration of the parameter space for the dark haloes by fitting the rotation curves of halo profiles with the exponential disk for stellar mass to that of MOND. In addition, we find that the baryon mass to the halo mass ratio is lower than the primordial ratio which gives that the total baryon mass is about 15% of the dark matter, and which is consistent with what we generally expect today.

  7. Polypoid Spitz Nevus With a Halo Reaction.

    PubMed

    Fernandez-Flores, Angel; Saeb-Lima, Marcela; Rodriguez-Peralto, José Luis

    2017-02-01

    Approximately, 2% of Spitz nevi are polypoid; between 3.6% and 7.4% present with a halo reaction. In tandem, these low percentages make the presence of a polypoid Spitz nevus with a halo reaction uncommon; we have not found reports of any previous cases. In the current report, we present a polypoid Spitz nevus with a halo reaction on the back of a 10-year-old male and discuss the morphologic findings. The lesion showed preserved nuclear expression of BAP1. There was no immunohistochemical expression of BRAF and ALK, while the melanocytic cells expressed p16. Comparative genomic hybridization was performed, and no significant aberrations were found. Only 2 small losses were evidenced in chromosome 8. The patient has been followed now for 2 years with no recurrence.

  8. Halo cold dark matter and microlensing

    SciTech Connect

    Gates, Evalyn; Turner, Michael S.

    1993-12-01

    There is good evidence that most of the baryons in the Universe are dark and some evidence that most of the matter in the Universe is nonbaryonic with cold dark matter (cdm) being a promising possibility. We discuss expectations for the abundance of baryons and cdm in the halo of our galaxy and locally. We show that in plausible cdm models the local density of cdm is at least $10^{-25}\\gcmm3$. We also discuss what one can learn about the the local cdm density from microlensing of stars in the LMC by dark stars in the halo and, based upon a suite of reasonable two-component halo models, conclude that microlensing is not a sensitive probe of the local cdm density.

  9. Coulomb dissociation of one- and two-neutron halos in halo EFT

    NASA Astrophysics Data System (ADS)

    Acharya, Bijaya; Phillips, Daniel

    2013-10-01

    In neutron halo nuclei the neutron distribution extends significantly beyond the region occupied by the nuclear ``core.'' Halo effective field theory (Halo-EFT) exploits the consequent separation of scales in order to predict relationships between low-energy observables in these systems as a systematic expansion in Rcore /Rhalo . This talk will discuss results for the Coulomb dissociation of neutron halo nuclei in this framework. In particular, we consider the Coulomb dissociation of 19C. We compute the reduced transition probability (dB (E 1) / dE) for excitation of the bound-state neutrons to the continuum up to N2LO in the Halo-EFT expansion. By comparing the predcition with data from RIKEN we are able to extract accurate results for 19C's one-neutron separation energy and asymptotic normalization coefficient. Good agreement between data and Halo-EFT is also found for the longitudinal momentum distribution of 19C. Results from ongoing work to extend ths calculation to two-neutron halos will also be presented. Supported by the US Department of Energy under grant DE-FG02- 93ER40756.

  10. Galaxy halo occupation at high redshift

    NASA Astrophysics Data System (ADS)

    Bullock, James S.; Wechsler, Risa H.; Somerville, Rachel S.

    2002-01-01

    We discuss how current and future data on the clustering and number density of z~3 Lyman-break galaxies (LBGs) can be used to constrain their relationship to dark matter haloes. We explore a three-parameter model in which the number of LBGs per dark halo scales like a power law in the halo mass: N(M)=(M/M1)S for M>Mmin. Here, Mmin is the minimum mass halo that can host an LBG, M1 is a normalization parameter, associated with the mass above which haloes host more than one observed LBG, and S determines the strength of the mass-dependence. We show how these three parameters are constrained by three observable properties of LBGs: the number density, the large-scale bias and the fraction of objects in close pairs. Given these three quantities, the three unknown model parameters may be estimated analytically, allowing a full exploration of parameter space. As an example, we assume a ΛCDM cosmology and consider the observed properties of a recent sample of spectroscopically confirmed LBGs. We find that the favoured range for our model parameters is Mmin~=(0.4-8)×1010h- 1Msolar, M1~=(6-10)×1012h- 1Msolar, and 0.9<~S<~1.1. The preferred region in Mmin expands by an order of magnitude, and slightly shallower slopes are acceptable if the allowed range of bg is permitted to span all recent observational estimates. We also discuss how the observed clustering of LBGs as a function of luminosity can be used to constrain halo occupation, although because of current observational uncertainties we are unable to reach any strong conclusions. Our methods and results can be used to constrain more realistic models that aim to derive the occupation function N(M) from first principles, and offer insight into how basic physical properties affect the observed properties of LBGs.

  11. The dark halo of the milky Way

    PubMed

    Alcock

    2000-01-07

    Most of the matter in the Milky Way is invisible to astronomers. Precise numbers are elusive, but it appears that the dark component is 20 times as massive as the visible disk of stars and gas. This dark matter is distributed in space differently than the stars, forming a vast, diffuse halo, more spherical than disklike, which occupies more than 1000 times the volume of the disk of stars. The composition of this dark halo is unknown, but it may comprise a mixture of ancient, degenerate dwarf stars and exotic, hypothetical elementary particles.

  12. Dark energy and extended dark matter halos

    NASA Astrophysics Data System (ADS)

    Chernin, A. D.; Teerikorpi, P.; Valtonen, M. J.; Dolgachev, V. P.; Domozhilova, L. M.; Byrd, G. G.

    2012-03-01

    The cosmological mean matter (dark and baryonic) density measured in the units of the critical density is Ωm = 0.27. Independently, the local mean density is estimated to be Ωloc = 0.08-0.23 from recent data on galaxy groups at redshifts up to z = 0.01-0.03 (as published by Crook et al. 2007, ApJ, 655, 790 and Makarov & Karachentsev 2011, MNRAS, 412, 2498). If the lower values of Ωloc are reliable, as Makarov & Karachentsev and some other observers prefer, does this mean that the Local Universe of 100-300 Mpc across is an underdensity in the cosmic matter distribution? Or could it nevertheless be representative of the mean cosmic density or even be an overdensity due to the Local Supercluster therein. We focus on dark matter halos of groups of galaxies and check how much dark mass the invisible outer layers of the halos are able to host. The outer layers are usually devoid of bright galaxies and cannot be seen at large distances. The key factor which bounds the size of an isolated halo is the local antigravity produced by the omnipresent background of dark energy. A gravitationally bound halo does not extend beyond the zero-gravity surface where the gravity of matter and the antigravity of dark energy balance, thus defining a natural upper size of a system. We use our theory of local dynamical effects of dark energy to estimate the maximal sizes and masses of the extended dark halos. Using data from three recent catalogs of galaxy groups, we show that the calculated mass bounds conform with the assumption that a significant amount of dark matter is located in the invisible outer parts of the extended halos, sufficient to fill the gap between the observed and expected local matter density. Nearby groups of galaxies and the Virgo cluster have dark halos which seem to extend up to their zero-gravity surfaces. If the extended halo is a common feature of gravitationally bound systems on scales of galaxy groups and clusters, the Local Universe could be typical or even

  13. Rockstar: Phase-space halo finder

    NASA Astrophysics Data System (ADS)

    Behroozi, Peter; Wechsler, Risa; Wu, Hao-Yi

    2012-10-01

    Rockstar (Robust Overdensity Calculation using K-Space Topologically Adaptive Refinement) identifies dark matter halos, substructure, and tidal features. The approach is based on adaptive hierarchical refinement of friends-of-friends groups in six phase-space dimensions and one time dimension, which allows for robust (grid-independent, shape-independent, and noise-resilient) tracking of substructure. Our method is massively parallel (up to 10^5 CPUs) and runs on the largest current simulations (>10^10 particles) with high efficiency (10 CPU hours and 60 gigabytes of memory required per billion particles analyzed). Rockstar offers significant improvement in substructure recovery as compared to several other halo finders.

  14. PHYSICAL PROPERTIES OF COMPLEX C HALO CLOUDS

    SciTech Connect

    Hsu, W.-H.; Putman, M. E.; Peek, J. E. G.; Heitsch, F.; Clark, S. E.; Stanimirovic, S.

    2011-02-15

    Observations from the Galactic Arecibo L-band Feed Array H I (GALFA-H I) Survey of the tail of Complex C are presented and the halo clouds associated with this complex are cataloged. The properties of the Complex C clouds are compared to clouds cataloged at the tail of the Magellanic Stream to provide insight into the origin and destruction mechanism of Complex C. Magellanic Stream and Complex C clouds show similarities in their mass distributions (slope = -0.7 and -0.6 log (N( log (mass)))/ log (mass), respectively) and have a common line width of 20-30 km s{sup -1} (indicative of a warm component), which may indicate a common origin and/or physical process breaking down the clouds. The clouds cataloged at the tail of Complex C extend over a mass range of 10{sup 1.1}-10{sup 4.8} M{sub sun}, sizes of 10{sup 1.2}-10{sup 2.6} pc, and have a median volume density and pressure of 0.065 cm{sup -3} and (P/k) = 580 K cm{sup -3}. We do not see a prominent two-phase structure in Complex C, possibly due to its low metallicity and inefficient cooling compared to other halo clouds. Assuming that the Complex C clouds are in pressure equilibrium with a hot halo medium, we find a median halo density of 5.8 x 10{sup -4} cm{sup -3}, which given a constant distance of 10 kpc is at a z-height of {approx}3 kpc. Using the same argument for the Stream results in a median halo density of 8.4 x 10-{sup 5} (60 kpc/d) cm{sup -3}. These densities are consistent with previous observational constraints and cosmological simulations. We also assess the derived cloud and halo properties with three-dimensional grid simulations of halo H I clouds and find that the temperature is generally consistent within a factor of 1.5 and the volume densities, pressures, and halo densities are consistent within a factor of three.

  15. Basilar impression in osteogenesis imperfecta: can it be treated with halo traction and posterior fusion?

    PubMed

    Noske, D P; van Royen, B J; Bron, J L; Vandertop, W P

    2006-12-01

    Basilar impression (BI) and hydrocephalus complicating osteogenesis imperfecta (OI) is usually treated by anterior transoral decompression and posterior fixation. Nevertheless, it may be questioned if posterior fusion following axial halo traction is adequate in patients with symptomatic BI complicating OI. We report on a case with progressive symptomatic hydrocephalus and BI complicating OI that was successfully treated by halo traction followed by posterior occipitocervical fusion. However, after a symptom free interval of 2 years the patient suffered from recurrence of symptomatic hydrocephalus needing additional ventriculoperitoneal (VP) shunt placement. In conclusion, posterior fusion without additional VP shunt placement may not be effective in the long term for ameliorating symptoms and signs and halting progressive hydrocephalus in BI complicating OI.

  16. THE STELLAR METALLICITY DISTRIBUTION FUNCTION OF THE GALACTIC HALO FROM SDSS PHOTOMETRY

    SciTech Connect

    An, Deokkeun; Beers, Timothy C.; Johnson, Jennifer A.; Pinsonneault, Marc H.; Lee, Young Sun; Bovy, Jo; Ivezic, Zeljko; Carollo, Daniela; Newby, Matthew

    2013-01-20

    We explore the stellar metallicity distribution function of the Galactic halo based on SDSS ugriz photometry. A set of stellar isochrones is calibrated using observations of several star clusters and validated by comparisons with medium-resolution spectroscopic values over a wide range of metal abundance. We estimate distances and metallicities for individual main-sequence stars in the multiply scanned SDSS Stripe 82, at heliocentric distances in the range 5-8 kpc and |b| > 35 Degree-Sign , and find that the in situ photometric metallicity distribution has a shape that matches that of the kinematically selected local halo stars from Ryan and Norris. We also examine independent kinematic information from proper-motion measurements for high Galactic latitude stars in our sample. We find that stars with retrograde rotation in the rest frame of the Galaxy are generally more metal poor than those exhibiting prograde rotation, which is consistent with earlier arguments by Carollo et al. that the halo system comprises at least two spatially overlapping components with differing metallicity, kinematics, and spatial distributions. The observed photometric metallicity distribution and that of Ryan and Norris can be described by a simple chemical evolution model by Hartwick (or by a single Gaussian distribution); however, the suggestive metallicity-kinematic correlation contradicts the basic assumption in this model that the Milky Way halo consists primarily of a single stellar population. When the observed metallicity distribution is deconvolved using two Gaussian components with peaks at [Fe/H] Almost-Equal-To -1.7 and -2.3, the metal-poor component accounts for {approx}20%-35% of the entire halo population in this distance range.

  17. Determination of the large scale volume weighted halo velocity bias in simulations

    NASA Astrophysics Data System (ADS)

    Zheng, Yi; Zhang, Pengjie; Jing, Yipeng

    2015-06-01

    A profound assumption in peculiar velocity cosmology is bv=1 at sufficiently large scales, where bv is the volume-weighted halo(galaxy) velocity bias with respect to the matter velocity field. However, this fundamental assumption has not been robustly verified in numerical simulations. Furthermore, it is challenged by structure formation theory (Bardeen, Bond, Kaiser and Szalay, Astrophys. J. 304, 15 (1986); Desjacques and Sheth, Phys. Rev D 81, 023526 (2010), which predicts the existence of velocity bias (at least for proto-halos) due to the fact that halos reside in special regions (local density peaks). The major obstacle to measuring the volume-weighted velocity from N-body simulations is an unphysical sampling artifact. It is entangled in the measured velocity statistics and becomes significant for sparse populations. With recently improved understanding of the sampling artifact (Zhang, Zheng and Jing, 2015, PRD; Zheng, Zhang and Jing, 2015, PRD), for the first time we are able to appropriately correct this sampling artifact and then robustly measure the volume-weighted halo velocity bias. (1) We verify bv=1 within 2% model uncertainty at k ≲0.1 h /Mpc and z =0 - 2 for halos of mass ˜1012- 1013h-1M⊙ and, therefore, consolidate a foundation for the peculiar velocity cosmology. (2) We also find statistically significant signs of bv≠1 at k ≳0.1 h /Mpc . Unfortunately, whether this is real or caused by a residual sampling artifact requires further investigation. Nevertheless, cosmology based on the k ≳0.1 h /Mpc velocity data should be careful with this potential velocity bias.

  18. Search for and analysis of radioactive halos in lunar material

    NASA Technical Reports Server (NTRS)

    Gentry, R. V.

    1976-01-01

    The lunar halo search was conducted because halos in terrestrial minerals serve as pointers to localized radioactivity, and make possible analytical studies on the problems of isotopic dating and mode of crystallization of the host mineral. Ancillary studies were conducted on terrestrial halos and on certain samples of special origin such as tektites and meteorites.

  19. The Constant Error of the Halo in Educational Outcomes Research.

    ERIC Educational Resources Information Center

    Pike, Gary R.

    1999-01-01

    Research suggests correlations between student gains and college experiences may be an artifact of halo effect. A study examined whether halo error underlies students' self-reported gains, significance of the error, and its effect on the relationship between college experiences and educational outcomes. Results confirm halo error may be an…

  20. Comment on Halo Effects in Rating and Evaluation Research.

    ERIC Educational Resources Information Center

    Feeley, Thomas Hugh

    2002-01-01

    Considers the existence of halo effects in individuals' evaluations of target communicators across different dimensions. Notes that halo effects result from raters' inability to discriminate among conceptually distinct and theoretically independent aspects of a target's behavior. Discusses current conceptions of halo error and suggests several…

  1. Comment on Halo Effects in Rating and Evaluation Research.

    ERIC Educational Resources Information Center

    Feeley, Thomas Hugh

    2002-01-01

    Considers the existence of halo effects in individuals' evaluations of target communicators across different dimensions. Notes that halo effects result from raters' inability to discriminate among conceptually distinct and theoretically independent aspects of a target's behavior. Discusses current conceptions of halo error and suggests several…

  2. The Constant Error of the Halo in Educational Outcomes Research.

    ERIC Educational Resources Information Center

    Pike, Gary R.

    1999-01-01

    Research suggests correlations between student gains and college experiences may be an artifact of halo effect. A study examined whether halo error underlies students' self-reported gains, significance of the error, and its effect on the relationship between college experiences and educational outcomes. Results confirm halo error may be an…

  3. DISCOVERY OF A GIANT RADIO HALO IN A NEW PLANCK GALAXY CLUSTER PLCKG171.9-40.7

    SciTech Connect

    Giacintucci, Simona; Kale, Ruta; Venturi, Tiziana; Wik, Daniel R.; Markevitch, Maxim

    2013-03-20

    We report the discovery of a giant radio halo in a new, hot, X-ray luminous galaxy cluster recently found by Planck, PLCKG171.9-40.7. The radio halo was found using Giant Metrewave Radio Telescope observations at 235 MHz and 610 MHz, and in the 1.4 GHz data from an NRAO Very Large Array Sky Survey pointing that we have reanalyzed. The diffuse radio emission is coincident with the cluster X-ray emission, and has an extent of {approx}1 Mpc and a radio power of {approx}5 Multiplication-Sign 10{sup 24} W Hz{sup -1} at 1.4 GHz. Its integrated radio spectrum has a slope of {alpha} Almost-Equal-To 1.8 between 235 MHz and 1.4 GHz, steeper than that of a typical giant halo. The analysis of the archival XMM-Newton X-ray data shows that the cluster is hot ({approx}10 keV) and disturbed, consistent with X-ray-selected clusters hosting radio halos. This is the first giant radio halo discovered in one of the new clusters found by Planck.

  4. Sign On to Computers: A Dictionary of Computer Signs.

    ERIC Educational Resources Information Center

    Zier, Cathy Diane; And Others

    This manual defines basic computer terminology and presents sign language gestures for the terms. The manual uses the Atlanta Area School for the Deaf's Manually Coded English Sign Language System, a compilation of signs derived from Signing Exact English and American Sign Language; it also indicates those instances where fingerspelling is…

  5. IDENTIFYING CONTRIBUTIONS TO THE STELLAR HALO FROM ACCRETED, KICKED-OUT, AND IN SITU POPULATIONS

    SciTech Connect

    Sheffield, Allyson A.; Johnston, Kathryn V.; Majewski, Steven R. E-mail: kvj@astro.columbia.edu; and others

    2012-12-20

    We present a medium-resolution spectroscopic survey of late-type giant stars at mid-Galactic latitudes of (30 Degree-Sign < |b| < 60 Degree-Sign ), designed to probe the properties of this population to distances of {approx}9 kpc. Because M giants are generally metal-rich and we have limited contamination from thin disk stars by the latitude selection, most of the stars in the survey are expected to be members of the thick disk (([Fe/H]) {approx} -0.6) with some contribution from the metal-rich component of the nearby halo. Here we report first results for 1799 stars. The distribution of radial velocity (RV) as a function of l for these stars shows (1) the expected thick disk population and (2) local metal-rich halo stars moving at high speeds relative to the disk, which in some cases form distinct sequences in RV-l space. High-resolution echelle spectra taken for 34 of these ''RV outliers'' reveal the following patterns across the [Ti/Fe]-[Fe/H] plane: 17 of the stars have abundances reminiscent of the populations present in dwarf satellites of the Milky Way, 8 have abundances coincident with those of the Galactic disk and a more metal-rich halo, and 9 of the stars fall on the locus defined by the majority of stars in the halo. The chemical abundance trends of the RV outliers suggest that this sample consists predominantly of stars accreted from infalling dwarf galaxies. A smaller fraction of stars in the RV outlier sample may have been formed in the inner Galaxy and subsequently kicked to higher eccentricity orbits, but the sample is not large enough to distinguish conclusively between this interpretation and the alternative that these stars represent the tail of the velocity distribution of the thick disk. Our data do not rule out the possibility that a minority of the sample could have formed from gas in situ on their current orbits. These results are consistent with scenarios where the stellar halo, at least as probed by M giants, arises from multiple

  6. Spoken Language Activation Alters Subsequent Sign Language Activation in L2 Learners of American Sign Language.

    PubMed

    Williams, Joshua T; Newman, Sharlene D

    2017-02-01

    A large body of literature has characterized unimodal monolingual and bilingual lexicons and how neighborhood density affects lexical access; however there have been relatively fewer studies that generalize these findings to bimodal (M2) second language (L2) learners of sign languages. The goal of the current study was to investigate parallel language activation in M2L2 learners of sign language and to characterize the influence of spoken language and sign language neighborhood density on the activation of ASL signs. A priming paradigm was used in which the neighbors of the sign target were activated with a spoken English word and compared the activation of the targets in sparse and dense neighborhoods. Neighborhood density effects in auditory primed lexical decision task were then compared to previous reports of native deaf signers who were only processing sign language. Results indicated reversed neighborhood density effects in M2L2 learners relative to those in deaf signers such that there were inhibitory effects of handshape density and facilitatory effects of location density. Additionally, increased inhibition for signs in dense handshape neighborhoods was greater for high proficiency L2 learners. These findings support recent models of the hearing bimodal bilingual lexicon, which posit lateral links between spoken language and sign language lexical representations.

  7. Signs of Overload

    MedlinePlus

    ... Listen Text Size Email Print Share Signs of Overload Page Content Article Body Although stress is a ... 12 (Copyright © 2004 American Academy of Pediatrics) The information contained on this Web site should not be ...

  8. Dermatomyositis: Signs and Symptoms

    MedlinePlus

    ... Meet our Partners How to Get Involved Donate Dermatomyositis (DM) Share print email share facebook twitter google ... Signs and Symptoms What happens to someone with dermatomyositis? For many decades, DM was considered “ polymyositis with ...

  9. Signs and Symptoms (Smallpox)

    MedlinePlus

    ... Smallpox Website NIH Smallpox Research CDC Poxvirus and Rabies Branch Poxvirus Diseases Signs and Symptoms Recommend on ... Smallpox Website NIH Smallpox Research CDC Poxvirus and Rabies Branch Poxvirus Diseases File Formats Help: How do ...

  10. Stop Sign Crater

    NASA Image and Video Library

    2003-03-06

    With its rim eroded off by catastrophic floods in Tiu Vallis and its strangely angular shape, this 12 km about 7.5 mile diameter crater imaged by NASA Mars Odyssey spacecraft looks vaguely like a stop sign.

  11. MENTOR/PROTEGE SIGNING

    NASA Image and Video Library

    2015-12-07

    MENTOR PROTÉGÉ AGREEMENT SIGNING CEREMONY, DECEMBER 7, 2015 L TO R STANDING: STEVE MILEY, TYLER COCHRAN, STEVE WOFFORD, DAVID BROCK (ALL NASA) L TO R SEATED: DANIEL ADAMSKI (AEROJET ROCKETDYNE), JOE MCCOLLISTER (NASA), EDWINA CIOFFI (ICO RALLY)

  12. Structure of Halo and Quasi-halo Helium-Helium-Alkali Trimers

    NASA Astrophysics Data System (ADS)

    Stipanović, Petar; Markić, Leandra Vranješ; Boronat, Jordi

    2017-05-01

    We report a diffusion Monte Carlo study of A^4He_2 and A^4He^3He trimers' structural properties, were A is one of the alkali atoms ^{6,7}Li, ^{23}Na, ^{39}K, ^{85}Rb or ^{133}Cs. Some of them are in a pure halo state, characterized by large spatial extent and universality, while some are close to the halo limit. The theoretical analysis of these trimers enables insight on how structural properties of weakly bound systems change when approaching the halo edge. For that purpose, two-variable distributions of inter-particle separations and angles were calculated. Extreme spatial extensions of some trimers with ^3He confirm their halo nature. Although all the considered systems are floppy, trimers with all bound dimer subsystems are less spread and have significantly lower percentage of quasi-linear configurations than those which have at least one unbound dimer subsystem.

  13. Detecting Signs of Intrusion.

    DTIC Science & Technology

    1997-08-01

    your systems, you should investigate any warnings they sound. Although monitors are not fool- proof, they can be part of an effective early warning ...Carnegie Mellon University Software Engineering Institute Detecting Signs of Intrusion Robert Firth Gary Ford Barbara Fräser John Kochmar...1997 Detecting Signs of Intrusion Robert Firth Gary Ford Barbara Fräser John Kochmar Suresh Konda John Richael Derek Simmel Networked Systems

  14. Reputation, Halo, and Ratings of Counseling Programs

    ERIC Educational Resources Information Center

    Thoreson, Richard W.; And Others

    1975-01-01

    This study tests the hypothesis that previous ratings of programs in psychology reflect both an experimental psychology and general institutional halo bias. It was found that applied programs in counseling psychology do receive ratings that differ from overall ratings of psychology in general. Programs ranked as strong, good, and adequate are…

  15. Reputation, Halo, and Ratings of Counseling Programs

    ERIC Educational Resources Information Center

    Thoreson, Richard W.; And Others

    1975-01-01

    This study tests the hypothesis that previous ratings of programs in psychology reflect both an experimental psychology and general institutional halo bias. It was found that applied programs in counseling psychology do receive ratings that differ from overall ratings of psychology in general. Programs ranked as strong, good, and adequate are…

  16. The Hot Gaseous Halos of Spiral Galaxies

    NASA Astrophysics Data System (ADS)

    Bregman, J.

    2016-06-01

    In the Milky Way, absorption and emission line measurements of O VII and O VIII show that the halo environment is dominated by a nearly spherical halo of temperature 2 × 10^6 K, metallicity of 0.3-0.5 solar, and with a density decreasing as r^{-3/2}. The mass of the hot gas, estimated through extrapolation to the virial radius, is comparable to the stellar mass, but does not account for the missing mass. The Milky Way hot halo appears to be rotating at about 180 km/s, which is consistent with model expectations, depending on the time of infall. Around massive spiral galaxies, hot halos are seen in emission out to about 70 kpc in the best cases. These show similar gas density laws and metallicities in the range 0.1-0.5 solar. The gas mass is comparable to the stellar mass, but does not account for the missing baryons within the virial radius. If the density law can be extrapolated to about three virial radii, the missing baryons would be accounted for.

  17. Substructure of fuzzy dark matter haloes

    NASA Astrophysics Data System (ADS)

    Du, Xiaolong; Behrens, Christoph; Niemeyer, Jens C.

    2017-02-01

    We derive the halo mass function (HMF) for fuzzy dark matter (FDM) by solving the excursion set problem explicitly with a mass-dependent barrier function, which has not been done before. We find that compared to the naive approach of the Sheth-Tormen HMF for FDM, our approach has a higher cutoff mass and the cutoff mass changes less strongly with redshifts. Using merger trees constructed with a modified version of the Lacey & Cole formalism that accounts for suppressed small-scale power and the scale-dependent growth of FDM haloes and the semi-analytic GALACTICUS code, we study the statistics of halo substructure including the effects from dynamical friction and tidal stripping. We find that if the dark matter is a mixture of cold dark matter (CDM) and FDM, there will be a suppression on the halo substructure on small scales which may be able to solve the missing satellites problem faced by the pure CDM model. The suppression becomes stronger with increasing FDM fraction or decreasing FDM mass. Thus, it may be used to constrain the FDM model.

  18. WEIGHING THE GALACTIC DARK MATTER HALO: A LOWER MASS LIMIT FROM THE FASTEST HALO STAR KNOWN

    SciTech Connect

    Przybilla, Norbert; Tillich, Alfred; Heber, Ulrich; Scholz, Ralf-Dieter

    2010-07-20

    The mass of the Galactic dark matter halo is under vivid discussion. A recent study by Xue et al. revised the Galactic halo mass downward by a factor of {approx}2 relative to previous work, based on the line-of-sight velocity distribution of {approx}2400 blue horizontal-branch (BHB) halo stars. The observations were interpreted with a statistical approach using cosmological galaxy formation simulations, as only four of the six-dimensional phase-space coordinates were determined. Here we concentrate on a close investigation of the stars with the highest negative radial velocity from that sample. For one star, SDSSJ153935.67+023909.8 (J1539+0239 for short), we succeed in measuring a significant proper motion, i.e., full phase-space information is obtained. We confirm the star to be a Population II BHB star from an independent quantitative analysis of the Sloan Digital Sky Survey (SDSS) spectrum-providing the first non-LTE (NLTE) study of any halo BHB star-and reconstruct its three-dimensional trajectory in the Galactic potential. J1539+0239 turns out to be the fastest halo star known to date, with a Galactic rest-frame velocity of 694{sup +300}{sub -221} km s{sup -1} (full uncertainty range from Monte Carlo error propagation) at its current position. The extreme kinematics of the star allows a significant lower limit to be put on the halo mass in order to keep it bound, of M {sub halo} {>=} 1.7{sup +2.3}{sub -1.1} x 10{sup 12} M{sub sun}. We conclude that the Xue et al. results tend to underestimate the true halo mass as their most likely mass value is consistent with our analysis only at a level of 4%. However, our result confirms other studies that make use of the full phase-space information.

  19. Non-Gaussian halo mass function and non-spherical halo collapse: theory vs. simulations

    SciTech Connect

    Achitouv, Ixandra E.; Corasaniti, Pier Stefano E-mail: Pier-Stefano.Corasaniti@obspm.fr

    2012-02-01

    The mass distribution of dark matter halos is a sensitive probe of primordial non-Gaussianity (NG). We derive an analytical formula of the halo mass function by perturbatively computing excursion set path-integrals for a non-Gaussian density field with non-vanishing skewness, f{sub NL}. We assume a stochastic barrier model which captures the main features of the ellipsoidal collapse of halos. Contrary to previous results based on extensions of the Press-Schechter formalism to NG initial conditions, we find that the non-spherical collapse of halos directly alter the signature of primordial NG. This points toward a potential degeneracy between the effect of primordial non-Gaussianity and that of non-linear halo collapse. The inferred mass function is found to be in remarkable agreement with N-body simulations of NG local type. Deviations are well within numerical uncertainties for all values of f{sub NL}{sup loc} in the range of validity of the perturbative calculation (|f{sub nl}{sup loc}|∼<200). Moreover, the comparison with simulation results suggests that for |f{sub NL}|∼>30 the non-linear collapse of halos, as described by our barrier model, strongly deviates from that of Gaussian initial conditions. This is not surprising since the effect of non-linear gravitational processes may be altered by initially large NG. Hence, in the lack of prior theoretical knowledge, halo collapse model parameters should be included in statistical halo mass function data analysis which aim to constrain the signature of primordial NG.

  20. The velocity shear tensor: tracer of halo alignment

    NASA Astrophysics Data System (ADS)

    Libeskind, Noam I.; Hoffman, Yehuda; Forero-Romero, Jaime; Gottlöber, Stefan; Knebe, Alexander; Steinmetz, Matthias; Klypin, Anatoly

    2013-01-01

    The alignment of dark matter (DM) haloes and the surrounding large-scale structure (LSS) is examined in the context of the cosmic web. Halo spin, shape and the orbital angular momentum of subhaloes are investigated relative to the LSS using the eigenvectors of the velocity shear tensor evaluated on a grid with a scale of 1 Mpc h-1, deep within the non-linear regime. Knots, filaments, sheets and voids are associated with regions that are collapsing along 3, 2, 1 or 0 principal directions simultaneously. Each halo is tagged with a web classification (i.e. knot halo, filament halo, etc.) according to the nature of the collapse at the halo position. The full distribution of shear eigenvalues is found to be substantially different from that tagged to haloes, indicating that the observed velocity shear is significantly biased. We find that larger mass haloes live in regions where the shear is more isotropic, namely the expansion or collapse is more spherical. A correlation is found between the halo shape and the eigenvectors of the shear tensor, with the longest (shortest) axis of the halo shape being aligned with the slowest (fastest) collapsing eigenvector. This correlation is web independent, suggesting that the velocity shear is a fundamental tracer of the halo alignment. A similar result is found for the alignment of halo spin with the cosmic web. It has been shown that high-mass haloes exhibit a spin flip with respect to the LSS: we find that the mass at which this spin flip occurs is web dependent and not universal as suggested previously. Although weaker than haloes, subhalo orbits too exhibit an alignment with the LSS, providing a possible insight into the highly correlated corotation of the Milky Way's satellite system. The present study suggests that the velocity shear tensor constitutes the natural framework for studying the directional properties of the non-linear LSS and those of haloes and galaxies.

  1. Stellar discs in Aquarius dark matter haloes

    NASA Astrophysics Data System (ADS)

    DeBuhr, Jackson; Ma, Chung-Pei; White, Simon D. M.

    2012-10-01

    We investigate the gravitational interactions between live stellar discs and their dark matter haloes, using Λ cold dark matter haloes similar in mass to that of the Milky Way taken from the Aquarius Project. We introduce the stellar discs by first allowing the haloes to respond to the influence of a growing rigid disc potential from z = 1.3 to 1.0. The rigid potential is then replaced with star particles which evolve self-consistently with the dark matter particles until z = 0.0. Regardless of the initial orientation of the disc, the inner parts of the haloes contract and change from prolate to oblate as the disc grows to its full size. When the disc's normal is initially aligned with the major axis of the halo at z = 1.3, the length of the major axis contracts and becomes the minor axis by z = 1.0. Six out of the eight discs in our main set of simulations form bars, and five of the six bars experience a buckling instability that results in a sudden jump in the vertical stellar velocity dispersion and an accompanying drop in the m = 2 Fourier amplitude of the disc surface density. The bars are not destroyed by the buckling but continue to grow until the present day. Bars are largely absent when the disc mass is reduced by a factor of 2 or more; the relative disc-to-halo mass is therefore a primary factor in bar formation and evolution. A subset of the discs is warped at the outskirts and contains prominent non-coplanar material with a ring-like structure. Many discs reorient by large angles between z = 1 and 0, following a coherent reorientation of their inner haloes. Larger reorientations produce more strongly warped discs, suggesting a tight link between the two phenomena. The origins of bars and warps appear independent: some discs with strong bars show little disturbances at the outskirts, while the discs with the weakest bars show severe warps.

  2. Mapping Dark Matter Halos with Stellar Kinematics

    NASA Astrophysics Data System (ADS)

    Murphy, Jeremy; Gebhardt, K.; Greene, J. E.; Graves, G.

    2013-07-01

    Galaxies of all sizes form and evolve in the centers of dark matter halos. As these halos constitute the large majority of the total mass of a galaxy, dark matter certainly plays a central role in the galaxy's formation and evolution. Yet despite our understanding of the importance of dark matter, observations of the extent and shape of dark matter halos have been slow in coming. The paucity of data is particularly acute in elliptical galaxies. Happily, concerted effort over the past several years by a number of groups has been shedding light on the dark matter halos around galaxies over a wide range in mass. The development of new instrumentation and large surveys, coupled with the tantalizing evidence for a direct detection of dark matter from the AMS experiment, has brought on a golden age in the study of galactic scale dark matter halos. I report on results using extended stellar kinematics from integrated light to dynamically model massive elliptical galaxies in the local universe. I use the integral field power of the Mitchell Spectrograph to explore the kinematics of stars to large radii (R > 2.5 r_e). Once the line-of-sight stellar kinematics are measured, I employ orbit-based, axisymmetric dynamical modeling to explore a range of dark matter halo parameterizations. Globular cluster kinematics at even larger radii are used to further constrain the dynamical models. The dynamical models also return information on the anisotropy of the stars which help to further illuminate the primary formation mechanisms of the galaxy. Specifically, I will show dynamical modeling results for the first and second rank galaxies in the Virgo Cluster, M49 and M87. Although similar in total luminosity and ellipticity, these two galaxies show evidence for different dark matter halo shapes, baryon to dark matter fractions, and stellar anisotropy profiles. Moreover, the stellar velocity dispersion at large radii in M87 is significantly higher than the globular clusters at the same

  3. The Impact of Theoretical Uncertainties in the Halo Mass Function and Halo

    SciTech Connect

    Wu, Hao-Yi; Zentner, Andrew R.; Wechsler, Risa H.; /KIPAC, Menlo Park /SLAC /Pittsburgh U. /KIPAC, Menlo Park /SLAC

    2010-06-04

    We study the impact of theoretical uncertainty in the dark matter halo mass function and halo bias on dark energy constraints from imminent galaxy cluster surveys. We find that for an optical cluster survey like the Dark Energy Survey, the accuracy required on the predicted halo mass function to make it an insignificant source of error on dark energy parameters is {approx}1%. The analogous requirement on the predicted halo bias is less stringent ({approx}5%), particularly if the observable-mass distribution can be well constrained by other means. These requirements depend upon survey area but are relatively insensitive to survey depth. The most stringent requirements are likely to come from a survey over a significant fraction of the sky that aims to observe clusters down to relatively low mass, M{sub th}{approx} 10{sup 13.7} h{sup -1} M{sub sun}; for such a survey, the mass function and halo bias must be predicted to accuracies of {approx}0.5% and {approx}1%, respectively. These accuracies represent a limit on the practical need to calibrate ever more accurate halo mass and bias functions. We find that improving predictions for the mass function in the low-redshift and low-mass regimes is the most effective way to improve dark energy constraints.

  4. Comparing halo bias from abundance and clustering

    NASA Astrophysics Data System (ADS)

    Hoffmann, K.; Bel, J.; Gaztañaga, E.

    2015-06-01

    We model the abundance of haloes in the ˜(3 Gpc h-1)3 volume of the MICE Grand Challenge simulation by fitting the universal mass function with an improved Jackknife error covariance estimator that matches theory predictions. We present unifying relations between different fitting models and new predictions for linear (b1) and non-linear (c2 and c3) halo clustering bias. Different mass function fits show strong variations in their performance when including the low mass range (Mh ≲ 3 × 1012 M⊙ h-1) in the analysis. Together with fits from the literature, we find an overall variation in the amplitudes of around 10 per cent in the low mass and up to 50 per cent in the high mass (galaxy cluster) range (Mh > 1014 M⊙ h-1). These variations propagate into a 10 per cent change in b1 predictions and a 50 per cent change in c2 or c3. Despite these strong variations, we find universal relations between b1 and c2 or c3 for which we provide simple fits. Excluding low-mass haloes, different models fitted with reasonable goodness in this analysis, show per cent level agreement in their b1 predictions, but are systematically 5-10 per cent lower than the bias directly measured with two-point halo-mass clustering. This result confirms previous findings derived from smaller volumes (and smaller masses). Inaccuracies in the bias predictions lead to 5-10 per cent errors in growth measurements. They also affect any halo occupation distribution fitting or (cluster) mass calibration from clustering measurements.

  5. Parametrizing the stellar haloes of galaxies

    NASA Astrophysics Data System (ADS)

    D'Souza, Richard; Kauffman, Guinevere; Wang, Jing; Vegetti, Simona

    2014-09-01

    We study the stellar haloes of galaxies out to 70-100 kpc as a function of stellar mass and galaxy type by stacking aligned r- and g-band images from a sample of 45 508 galaxies from Sloan Digital Sky Survey Data Release 9 in the redshift range 0.06 ≤ z ≤ 0.1 and in the mass range 1010.0 M⊙ < M* < 1011.4 M⊙. We derive surface brightness profiles to a depth of almost μr ˜ 32 mag arcsec-2. We find that the ellipticity of the stellar halo is a function of galaxy stellar mass and that the haloes of high-concentration galaxies are more elliptical than those of low-concentration galaxies. Where the g - r colour of the stellar halo can be measured, we find that the stellar light is always bluer than in the main galaxy. The colour of the stellar halo is redder for more massive galaxies. We further demonstrate that the full two-dimensional surface intensity distribution of our galaxy stacks can only be fit through multicomponent Sérsic models. Using the fraction of light in the outer component of the models as a proxy for the fraction of accreted stellar light, we show that this fraction is a function of stellar mass and galaxy type. The fraction of accreted stellar light rises from 30 to 70 per cent and from 2 to 25 per cent for high- and low-concentration galaxies, respectively, over the mass range 1010.0-1011.4 M⊙.

  6. PEEK-Halo effect in interbody fusion.

    PubMed

    Phan, Kevin; Hogan, Jarred A; Assem, Yusuf; Mobbs, Ralph J

    2016-02-01

    Recent developments have seen poly[aryl-ether-ether-ketone] (PEEK) being increasingly used in vertebral body fusion. More novel approaches to improve PEEK have included the introduction of titanium-PEEK (Ti-PEEK) composites and coatings. This paper aims to describe a potential complication of PEEK based implants relating to poorer integration with the surrounding bone, producing a "PEEK-Halo" effect which is not seen in Ti-PEEK composite implants. We present images from two patients undergoing anterior lumbar interbody fusion (ALIF). The first patient underwent an L5/S1 ALIF using a PEEK implant whilst the second patient underwent L4/L5 ALIF using a Ti-PEEK composite implant. Evidence of osseointegration was sought using CT imaging and confirmed using histological preparations of a sheep tibia model. The PEEK-Halo effect is demonstrated by a halo effect between the PEEK implant and the bone graft on CT imaging. This phenomenon is secondary to poor osseointegration of PEEK implants. The PEEK-Halo effect was not demonstrated in the second patient who received a Ti-PEEK composite graft. Histological analysis of graft/bone interface surfaces in PEEK versus Ti-PEEK implants in a sheep model further confirmed poorer osseointegration of the PEEK implant. In conclusion, the PEEK-Halo effect is seen secondary to minimal osseointegration of PEEK at the adjacent vertebral endplate following a PEEK implant insertion. This effect is not seen with Ti-PEEK implants, and may support the role of titanium in improving the bone-implant interface of PEEK substrates. Copyright © 2015 Elsevier Ltd. All rights reserved.

  7. The Circumgalactic Medium in Massive Halos

    NASA Astrophysics Data System (ADS)

    Chen, Hsiao-Wen

    This chapter presents a review of the current state of knowledge on the cool (T ˜ 104 K) halo gas content around massive galaxies at z ≈ 0. 2-2. Over the last decade, significant progress has been made in characterizing the cool circumgalactic gas in massive halos of M h ≈ 1012-14 M⊙ at intermediate redshifts using absorption spectroscopy. Systematic studies of halo gas around massive galaxies beyond the nearby universe are made possible by large spectroscopic samples of galaxies and quasars in public archives. In addition to accurate and precise constraints for the incidence of cool gas in massive halos, detailed characterizations of gas kinematics and chemical compositions around massive quiescent galaxies at z ≈ 0. 5 have also been obtained. Combining all available measurements shows that infalling clouds from external sources are likely the primary source of cool gas detected at d 100 d\\gtrsim 100 kpc from massive quiescent galaxies. The origin of the gas closer in is currently less certain, but SNe Ia driven winds appear to contribute significantly to cool gas found at d < 100 kpc. In contrast, cool gas observed at d 200 d\\lesssim 200 kpc from luminous quasars appears to be intimately connected to quasar activities on parsec scales. The observed strong correlation between cool gas covering fraction in quasar host halos and quasar bolometric luminosity remains a puzzle. Combining absorption-line studies with spatially resolved emission measurements of both gas and galaxies is the necessary next step to address remaining questions.

  8. Dark Matter Halos with VIRUS-P

    NASA Astrophysics Data System (ADS)

    Murphy, Jeremy; Gebhardt, K.

    2010-05-01

    We present new, two-dimensional stellar kinematic data on several of the most massive galaxies in the local universe. These data were taken with the integral field spectrograph, VIRUS-P, and extend to unprecedented radial distances. Once robust stellar kinematics are in hand, we run orbit-based axisymmetric dynamical models in order to constrain the stellar mass-to-light ratio and dark matter halo parameters. We have run a large set of dynamical models on the second rank galaxy in the Virgo cluster, M87, and find clear evidence for a massive dark matter halo. The two-dimensional stellar kinematics for several of our other targets, all first and second rank galaxies, are also presented. Dark matter halos are known to dominate the mass profile of elliptical galaxies somewhere between one to two effective radii, yet due to the low surface brightness at these radial distances, determining stellar dynamics is technologically challenging. To overcome this, constraints on the dark matter halo are often made with planetary nebulae or globular clusters at large radii. However, as results from different groups have returned contradictory results, it remains unclear whether different dynamical tracers always follow the stellar kinematics. Due to VIRUS-P's large field of view and on-sky fiber diameter, we are able to determine stellar kinematics at radial distances that overlap with other dynamical tracers. Understanding what the dynamics of stars, planetary nebula and globular clusters tell us about both the extent of the dark matter halo profile and the formation histories of the largest elliptical galaxies is a primary science driver for this work.

  9. Highly-Ionized Gas in the Galactic Halo: A FUSE Survey of O 6 Absorption toward 22 Halo Stars

    NASA Astrophysics Data System (ADS)

    Zsargo, J.; Sembach, K. R.; Howk, J. C.; Savage, B. D.

    2002-12-01

    Far Ultraviolet Spectroscopic Explorer (FUSE) spectra of 22 Galactic halo stars are studied to determine the amount of O 6 in the Galactic halo between ~0.3 and ~10 kpc from the Galactic mid-plane. Strong O 6 λ 1031.93 absorption was detected toward 21 stars, and a reliable 3 σ upper limit was obtained toward HD 97991. The weaker member of the O 6 doublet at 1037.62 Å could be studied toward only six stars. The observed columns are reasonably consistent with a patchy exponential O 6 distribution with a mid-plane density of 1.7x10-8 cm-3 and scale height between 2.3 and 4 kpc. We do not see clear signs of strong high-velocity components in O 6 absorption along the Galactic sight lines, which indicates the general absence of high velocity O 6 within 2-5 kpc of the Galactic mid-plane. The correlation between the H 1 and O 6 intermediate velocity absorption is also poor. The O 6 velocity dispersions are much larger than the value of ~18 km/s expected from thermal broadening for gas at T ~ 3x105 K, the temperature at which O 6 is expected to reach its peak abundance in collisional ionization equilibrium. Turbulence, inflow, and outflow must have an effect on the shape of the O 6 profiles. Kinematical comparisons of O 6 with Ar 1 reveal that 9 of 21 sight lines are closely aligned in LSR velocity (|Δ VLSR| <=5 km/s ), while 8 of 21 exhibit significant velocity differences (|Δ VLSR| >= 15 km/s ). This dual behavior may indicate the presence of two different types of O 6-bearing environments toward the Galactic sight lines. Comparison of O 6 with other highly-ionized species suggests that the high ions are produced primarily by cooling hot gas in the Galactic fountain flow, and that turbulent mixing also has a significant contribution. The role of turbulent mixing is most important toward sight lines that sample supernova remnants like Loop I and IV. We are also able to show that the O 6 enhancement toward the Galactic center region that was observed in the FUSE

  10. Halo mass distribution reconstruction across the cosmic web

    NASA Astrophysics Data System (ADS)

    Zhao, Cheng; Kitaura, Francisco-Shu; Chuang, Chia-Hsun; Prada, Francisco; Yepes, Gustavo; Tao, Charling

    2015-08-01

    We study the relation between halo mass and its environment from a probabilistic perspective. We find that halo mass depends not only on local dark matter density, but also on non-local quantities such as the cosmic web environment and the halo-exclusion effect. Given these accurate relations, we have developed the HADRON-code (Halo mAss Distribution ReconstructiON), a technique which permits us to assign halo masses to a distribution of haloes in three-dimensional space. This can be applied to the fast production of mock galaxy catalogues, by assigning halo masses, and reproducing accurately the bias for different mass cuts. The resulting clustering of the halo populations agree well with that drawn from the BigMultiDark N-body simulation: the power spectra are within 1σ up to scales of k = 0.2 h Mpc-1, when using augmented Lagrangian perturbation theory based mock catalogues. Only the most massive haloes show a larger deviation. For these, we find evidence of the halo-exclusion effect. A clear improvement is achieved when assigning the highest masses to haloes with a minimum distance separation. We also compute the two- and three-point correlation functions, and find an excellent agreement with N-body results. Our work represents a quantitative application of the cosmic web classification. It can have further interesting applications in the multitracer analysis of the large-scale structure for future galaxy surveys.

  11. Characteristic time for halo current growth and rotation

    NASA Astrophysics Data System (ADS)

    Boozer, Allen H.

    2015-10-01

    A halo current flows for part of its path through the plasma edge and for part through the chamber walls and during tokamak disruptions can be as large as tenths of the plasma current. The primary interest in halo currents is the large force that they can exert on machine components particularly if the toriodal rotation of the halo current resonates with a natural oscillation frequency of the tokamak device. Halo currents arise when required to slow down the growth of a kink that is too unstable to be stabilized by the chamber walls. The width of the current channel in the halo plasma is comparable to the amplitude of the kink, and the halo current grows linearly, not exponentially, in time. The current density in the halo is comparable to that of the main plasma body. The rocket force due to plasma flowing out of the halo and recombining on the chamber walls can cause the non-axisymmetric magnetic structure produced by the kink to rotate toroidally at a speed comparable to the halo speed of sound. Gerhardt's observations of the halo current in NSTX shot 141 687 [Nucl. Fusion 53, 023005 (2013)] illustrate many features of the theory of halo currents and are discussed as a summary of the theory.

  12. Characteristic time for halo current growth and rotation

    SciTech Connect

    Boozer, Allen H.

    2015-10-15

    A halo current flows for part of its path through the plasma edge and for part through the chamber walls and during tokamak disruptions can be as large as tenths of the plasma current. The primary interest in halo currents is the large force that they can exert on machine components particularly if the toriodal rotation of the halo current resonates with a natural oscillation frequency of the tokamak device. Halo currents arise when required to slow down the growth of a kink that is too unstable to be stabilized by the chamber walls. The width of the current channel in the halo plasma is comparable to the amplitude of the kink, and the halo current grows linearly, not exponentially, in time. The current density in the halo is comparable to that of the main plasma body. The rocket force due to plasma flowing out of the halo and recombining on the chamber walls can cause the non-axisymmetric magnetic structure produced by the kink to rotate toroidally at a speed comparable to the halo speed of sound. Gerhardt's observations of the halo current in NSTX shot 141 687 [Nucl. Fusion 53, 023005 (2013)] illustrate many features of the theory of halo currents and are discussed as a summary of the theory.

  13. Dynamics of the Disruption Halo Current Toroidal Asymmetry in NSTX

    SciTech Connect

    S.P. Gerhardt

    2012-09-27

    This paper describes the dynamics of disruption halo current non-axisymmetries in the lower divertor of the National Spherical Torus Experiment [M. Ono, et al. Nuclear Fusion 40, 557 (2000)]. While. The halo currents typically have a strongly asymmetric structure where they enter the divertor floor, and this asymmetry has been observed to complete up to 7 toroidal revolutions over the duration of the halo current pulse. However, the rotation speed and toroidal extend of the asymmetry can vary significantly during the pulse. The rotation speed, halo current pulse duration, and total number of revolutions tend to be smaller in cases with large halo currents. The halo current pattern is observed to become toroidally symmetric at the end of the halo current pulse. It is proposed that this symmeterization is due to the loss of most or all of the closed field line geometry in the final phase of the vertical displacement event.

  14. ORIGAMI: DELINEATING HALOS USING PHASE-SPACE FOLDS

    SciTech Connect

    Falck, Bridget L.; Neyrinck, Mark C.; Szalay, Alexander S.

    2012-08-01

    We present the ORIGAMI method of identifying structures, particularly halos, in cosmological N-body simulations. Structure formation can be thought of as the folding of an initially flat three-dimensional manifold in six-dimensional phase space. ORIGAMI finds the outer folds that delineate these structures. Halo particles are identified as those that have undergone shell-crossing along three orthogonal axes, providing a dynamical definition of halo regions that is independent of density. ORIGAMI also identifies other morphological structures: particles that have undergone shell-crossing along 2, 1, or 0 orthogonal axes correspond to filaments, walls, and voids, respectively. We compare this method to a standard friends-of-friends halo-finding algorithm and find that ORIGAMI halos are somewhat larger, more diffuse, and less spherical, though the global properties of ORIGAMI halos are in good agreement with other modern halo-finding algorithms.

  15. Can MACHOs probe the shape of the galaxy halo ?

    NASA Technical Reports Server (NTRS)

    Frieman, Joshua; Scoccimarro, Roman

    1994-01-01

    Microlensing searches in our galaxy have recently discovered several candidates in the direction of the Large Magellanic Cloud (LMC). We study the prospects for such searches to yield useful information about the flattening of the Galaxy dark matter halo, using a self-consistent oblate halo model and allowing for the possibility of misalignment between the disk and halo symmetry axes. The microlensing optical depth for the LMC, tau(LMC), depends sensitively on the disk-halo tilt angle in the Milky Way, as does the ratio tau(SMC)/tau(LMC). If the tilt angle is as large as 30 deg, a much larger spread in values for tau(LMC) is consistent with rotation curve constraints than previously thought. Disk-halo tilt and halo flattening do not significantly affect the massive compact halo object (MACHO) masses inferred from event durations.

  16. The global dark halo structure of the Andromeda galaxy

    NASA Astrophysics Data System (ADS)

    Hayashi, Kohei; Chiba, Masashi

    2014-01-01

    We set new limits on the global shape of the dark halo in the Andromeda galaxy based on axisymmetric mass models constructed by Hayashi & Chiba (2012). This is motivated by the fact that CDM models predict non-spherical virialized dark halos, which reflect the process of mass assembly in the galactic scale. Based on the application of our models to latest kinematical data of globular clusters and dwarf spheroidal galaxies in the Andromeda halo, we find that the most plausible cases for Andromeda yield not a spherical but a prolate shape for its dark halo. We also find that the prolate dark halo is consistent with theoretical predictions in which the satellites are distributed anisotropically and preferentially located along major axes of their galactic host halos. It is a reflection of the intimate connection between galactic dark matter halos and the cosmic web.

  17. Low frequency follow up of radio haloes and relics in the GMRT Radio Halo Cluster Survey

    NASA Astrophysics Data System (ADS)

    Venturi, T.; Giacintucci, S.; Dallacasa, D.; Cassano, R.; Brunetti, G.; Macario, G.; Athreya, R.

    2013-03-01

    Aims: To gain insight into the origin of diffuse radio sources in galaxy clusters and their connection with cluster merger processes, we performed GMRT low frequency observations of the radio haloes, relics and new candidates belonging to the GMRT radio Halo cluster sample first observed at 610 MHz. Our main aim was to investigate their observational properties and integrated spectra at frequencies below 610 MHz. Methods: High sensitivity imaging was performed using the GMRT at 325 MHz and 240 MHz. The properties of the diffuse emission in each cluster were compared to our 610 MHz images and/or literature information available at other frequencies, in order to derive the integrated spectra over a wide frequency range. Results: Cluster radio haloes form a composite class in terms of spectral properties. Beyond the classical radio haloes, whose spectral index α is in the range ~1.2 ÷ 1.3 (S ∝ ν- α), we found sources with α ~ 1.6 ÷ 1.9. This result supports the idea that the spectra of the radiating particles in radio haloes is not universal and that inefficient mechanisms of particle acceleration are responsible for their origin. We also found a variety of brightness distributions, i.e. both centrally peaked and clumpy haloes. Even though the thermal and relativistic plasma tend to occupy the same cluster volume, in some cases a positional shift between the radio and X-ray peaks of emission is evident. Our observations also revealed diffuse cluster sources that cannot be easily classified as either haloes or relics. New candidate relics were found in A 1300 and in A 1682, and in some clusters "bridges" of radio emission have been detected, connecting the relic and radio halo emission. Finally, by combining our new data with information in the literature, we derived the Log LX - Log P325 MHz correlation for radio haloes, and investigated the possible correlation of the spectral index of radio haloes with the temperature of the intracluster medium.

  18. Reversible dementias

    PubMed Central

    Tripathi, Manjari; Vibha, Deepti

    2009-01-01

    In recent years, more attention has been given to the early diagnostic evaluation of patients with dementia which is essential to identify patients with cognitive symptoms who may have treatable conditions. Guidelines suggest that all patients presenting with dementia or cognitive symptoms should be evaluated with a range of laboratory tests, and with structural brain imaging with computed tomography (CT) or magnetic resonance imaging (MRI). While many of the disorders reported as ‘reversible dementias’ are conditions that may well be associated with cognitive or behavioral symptoms, these symptoms are not always sufficiently severe to fulfill the clinical criteria for dementia. Thus, while the etiology of a condition may be treatable it should not be assumed that the associated dementia is fully reversible. Potentially reversible dementias should be identified and treatment considered, even if the symptoms are not sufficiently severe to meet the clinical criteria for dementia, and even if partial or full reversal of the cognitive symptoms cannot be guaranteed. In the literature, the most frequently observed potentially reversible conditions identified in patients with cognitive impairment or dementia are depression, adverse effects of drugs, drug or alcohol abuse, space-occupying lesions, normal pressure hydrocephalus, and metabolic conditions land endocrinal conditions like hypothyroidism and nutritional conditions like vitamin B-12 deficiency. Depression is by far the most common of the potentially reversible conditions. The review, hence addresses the common causes of reversible dementia and the studies published so far. PMID:21416018

  19. A Speeding Binary in the Galactic Halo

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2016-04-01

    The recent discovery of a hyper-velocity binary star system in the halo of the Milky Way poses a mystery: how was this system accelerated to its high speed?Accelerating StarsUnlike the uniform motion in the Galactic disk, stars in the Milky Ways halo exhibit a huge diversity of orbits that are usually tilted relative to the disk and have a variety of speeds. One type of halo star, so-called hyper-velocity stars, travel with speeds that can approach the escape velocity of the Galaxy.How do these hyper-velocity stars come about? Assuming they form in the Galactic disk, there are multiple proposed scenarios through which they could be accelerated and injected into the halo, such as:Ejection after a close encounter with the supermassive black hole at the Galactic centerEjection due to a nearby supernova explosionEjection as the result of a dynamical interaction in a dense stellar population.Further observations of hyper-velocity stars are necessary to identify the mechanism responsible for their acceleration.J1211s SurpriseModels of J1211s orbit show it did not originate from the Galactic center (black dot). The solar symbol shows the position of the Sun and the star shows the current position of J1211. The bottom two panels show two depictions(x-y plane and r-z plane) of estimated orbits of J1211 over the past 10 Gyr. [Nmeth et al. 2016]To this end, a team of scientists led by Pter Nmeth (Friedrich Alexander University, Erlangen-Nrnberg) recently studied the candidate halo hyper-velocity star SDSS J121150.27+143716.2. The scientists obtained spectroscopy of J1211 using spectrographs at the Keck Telescope in Hawaii and ESOs Very Large Telescope in Chile. To their surprise, they discovered the signature of a companion in the spectra: J1211 is actually a binary!Nmeth and collaborators found that J1211, located roughly 18,000 light-years away, is moving at a rapid ~570 km/s relative to the galactic rest frame. The binary system consists of a hot (30,600 K) subdwarf and a

  20. Hot Stars in the Galactic Halo

    NASA Astrophysics Data System (ADS)

    Adelman, Saul J.; Upgren, Arthur R.; Adelman, Carol J.

    2011-03-01

    Participants; Preface; Foreword; Acknowledgements; Part I. Introductory Papers: 1. What is the galaxy's halo population?; 2. Theoretical properties of horizontal-branch stars; 3. A review of A-type horizontal-branch stars; Part II. Surveys: 4. A progress report on the Edinburgh-Cape object survey; 5. A 300 square degree survey of young stars at high galactic latitudes; 6. The isolation of a new sample of B stars in the halo; 7. A northern catalog of FHB/A stars; 8. Recent progress on a continuing survey of galactic globular clusters for blue stragglers; 9. UV observations with FAUST and the galactic model; 10. Hot stars at the South Galactic Pole; Part III. Clusters: 11. Population II horizontal branches: a photometric study of globular clusters; 12. The period-shift effect in Oosterhoff type II globular clusters; 13. UV photometry of hot stars in omega centauri; 14. Spectroscopic and UBV observations of blue stars at the NGP; 15. Population I horizontal branches: probing the halo-to-disk transition; Part IV. Stars: 16. Very hot subdwarf O stars; 17. Quantitative spectroscopy of the very hot subluminous O-stars: K646, PG1159-035, and KPD0005+5106; 18. Analyzing the helium-rich hot sdO stars in the Palomar Green Survey; 19. Late type companions of hot sd O stars; 20. Hot stars in globular clusters; 21. Faint blue stars from the Hamburg Schmidt Survey; 22. Stellar winds and the evolution of sdB's to sdO's; 23. Halo stars in the Vilnius photometric system; 24. Horizontal branch stars in the geneva photometric system; 25. Zeeman observations of FHB stars and hot subdwarf stars; 26. What does a FHB star's spectrum look like?; 27. A technique for distinguishing FHB stars from A-type stars; 28. eEemental abundances of halo A and interloper stars; 29. The mass of blue horizontal branch stars in the globular cluster NGC6397; 30. IUE observations of blue HB stars in the globular clusters M3 and NGC6752; 31. Metallicities and kinematics of the local RR lyraes: lukewarm stars

  1. Hot Stars in the Galactic Halo

    NASA Astrophysics Data System (ADS)

    Adelman, Saul J.; Upgren, Arthur R.; Adelman, Carol J.

    1994-08-01

    Participants; Preface; Foreword; Acknowledgements; Part I. Introductory Papers: 1. What is the galaxy's halo population?; 2. Theoretical properties of horizontal-branch stars; 3. A review of A-type horizontal-branch stars; Part II. Surveys: 4. A progress report on the Edinburgh-Cape object survey; 5. A 300 square degree survey of young stars at high galactic latitudes; 6. The isolation of a new sample of B stars in the halo; 7. A northern catalog of FHB/A stars; 8. Recent progress on a continuing survey of galactic globular clusters for blue stragglers; 9. UV observations with FAUST and the galactic model; 10. Hot stars at the South Galactic Pole; Part III. Clusters: 11. Population II horizontal branches: a photometric study of globular clusters; 12. The period-shift effect in Oosterhoff type II globular clusters; 13. UV photometry of hot stars in omega centauri; 14. Spectroscopic and UBV observations of blue stars at the NGP; 15. Population I horizontal branches: probing the halo-to-disk transition; Part IV. Stars: 16. Very hot subdwarf O stars; 17. Quantitative spectroscopy of the very hot subluminous O-stars: K646, PG1159-035, and KPD0005+5106; 18. Analyzing the helium-rich hot sdO stars in the Palomar Green Survey; 19. Late type companions of hot sd O stars; 20. Hot stars in globular clusters; 21. Faint blue stars from the Hamburg Schmidt Survey; 22. Stellar winds and the evolution of sdB's to sdO's; 23. Halo stars in the Vilnius photometric system; 24. Horizontal branch stars in the geneva photometric system; 25. Zeeman observations of FHB stars and hot subdwarf stars; 26. What does a FHB star's spectrum look like?; 27. A technique for distinguishing FHB stars from A-type stars; 28. eEemental abundances of halo A and interloper stars; 29. The mass of blue horizontal branch stars in the globular cluster NGC6397; 30. IUE observations of blue HB stars in the globular clusters M3 and NGC6752; 31. Metallicities and kinematics of the local RR lyraes: lukewarm stars

  2. AN XMM-NEWTON SURVEY OF THE SOFT X-RAY BACKGROUND. III. THE GALACTIC HALO X-RAY EMISSION

    SciTech Connect

    Henley, David B.; Shelton, Robin L.

    2013-08-20

    We present measurements of the Galactic halo's X-ray emission for 110 XMM-Newton sight lines selected to minimize contamination from solar wind charge exchange emission. We detect emission from few million degree gas on {approx}4/5 of our sight lines. The temperature is fairly uniform (median = 2.22 Multiplication-Sign 10{sup 6} K, interquartile range = 0.63 Multiplication-Sign 10{sup 6} K), while the emission measure and intrinsic 0.5-2.0 keV surface brightness vary by over an order of magnitude ({approx}(0.4-7) Multiplication-Sign 10{sup -3} cm{sup -6} pc and {approx}(0.5-7) Multiplication-Sign 10{sup -12} erg cm{sup -2} s{sup -1} deg{sup -2}, respectively, with median detections of 1.9 Multiplication-Sign 10{sup -3} cm{sup -6} pc and 1.5 Multiplication-Sign 10{sup -12} erg cm{sup -2} s{sup -1} deg{sup -2}, respectively). The high-latitude sky contains a patchy distribution of few million degree gas. This gas exhibits a general increase in emission measure toward the inner Galaxy in the southern Galactic hemisphere. However, there is no tendency for our observed emission measures to decrease with increasing Galactic latitude, contrary to what is expected for a disk-like halo morphology. The measured temperatures, brightnesses, and spatial distributions of the gas can be used to place constraints on models for the dominant heating sources of the halo. We provide some discussion of such heating sources, but defer comparisons between the observations and detailed models to a later paper.

  3. Cryogenic ion implantation near amorphization threshold dose for halo/extension junction improvement in sub-30 nm device technologies

    SciTech Connect

    Park, Hugh; Todorov, Stan; Colombeau, Benjamin; Rodier, Dennis; Kouzminov, Dimitry; Zou Wei; Guo Baonian; Khasgiwale, Niranjan; Decker-Lucke, Kurt

    2012-11-06

    We report on junction advantages of cryogenic ion implantation with medium current implanters. We propose a methodical approach on maximizing cryogenic effects on junction characteristics near the amorphization threshold doses that are typically used for halo implants for sub-30 nm technologies. BF{sub 2}{sup +} implant at a dose of 8 Multiplication-Sign 10{sup 13}cm{sup -2} does not amorphize silicon at room temperature. When implanted at -100 Degree-Sign C, it forms a 30 - 35 nm thick amorphous layer. The cryogenic BF{sub 2}{sup +} implant significantly reduces the depth of the boron distribution, both as-implanted and after anneals, which improves short channel rolloff characteristics. It also creates a shallower n{sup +}-p junction by steepening profiles of arsenic that is subsequently implanted in the surface region. We demonstrate effects of implant sequences, germanium preamorphization, indium and carbon co-implants for extension/halo process integration. When applied to sequences such as Ge+As+C+In+BF{sub 2}{sup +}, the cryogenic implants at -100 Degree-Sign C enable removal of Ge preamorphization, and form more active n{sup +}-p junctions and steeper B and In halo profiles than sequences at room temperature.

  4. The Meaning of Signs:

    PubMed Central

    Stein, Claudia

    2006-01-01

    This article reconstructs the diagnostic act of the French pox in the French-disease hospital of sixteenth-century Augsburg. It focuses on how the participants in the clinical encounter imagined the configuration of the pox and its localization in the human body. Of central importance for answering this question is the early modern conception of physical signs. It has been argued that it was due to a specific understanding of bodily signs and their relationship to a disease and its causes, that disease definition and classification in the early modern period showed a high degree of flexibility and fluidity. This paper looks at how the sixteenth-century theoretical conception of physical signs not only shaped the diagnosis and treatment of the pox but also reflected the overall organization of institutions. PMID:17242549

  5. Vital Signs Rate Meter.

    DTIC Science & Technology

    1987-09-01

    S15 VITAL SIGNS RTE NETER(U) TEXAS R FW4D A UNIV COLLEGE 1/1 STATION IENGINEERING PROGM C S LESSAD ET RL. SEP 8? USRFSN-TR-$?-14 F33615-S3-D-0602...UNCLMSIFIED F/O 6/12 ML IIB 125 11 128 11.2.5_ ka7 U S S SS S S S S S0 02.2 36 * . * * * . - * . - .. . - - . Q -- .* USAFSAM-TR-87-1 4 VITAL SIGNS RATE...UNIT ELEMENT NO. INO.I NO. IACESSION NO. 622027 2729 02 21 11 TITLE ft ml’S111111:1111"ll vital Signs Rae ~t= 12. PERSONAL AUTWOR(S) Lessard, Cierles

  6. Intracranial halo pin penetration causing brain injury secondary to poor halo care technique: a case report and literature review

    PubMed Central

    Male, Kishore Reddy; Guha, Abhijit; James, Stuart; Ahuja, Sashin

    2008-01-01

    This is a case report of intra cranial penetration by halo pins resulting in cerebritis and fits secondary to incorrect halo care by the patient and his family. Halo pin penetration into the skull with brain injury is itself a rare incident. Previously documented case reports were in patients with a previous cranioplasties and they were highlight the fact that halo not to be used in cranioplasty patients. Cranial penetration of the halo pins has generally been secondary to a fall/medical condition as epilepsy. This incident how ever highlights the fact the halo care itself along with proper techniques used for tightening the halo pins by the carer plays a crucial role in preventing complications such as this. PMID:19068118

  7. Precise halo orbit design and optimal transfer to halo orbits from earth using differential evolution

    NASA Astrophysics Data System (ADS)

    Nath, Pranav; Ramanan, R. V.

    2016-01-01

    The mission design to a halo orbit around the libration points from Earth involves two important steps. In the first step, we design a halo orbit for a specified size and in the second step, we obtain an optimal transfer trajectory design to the halo orbit from an Earth parking orbit. Conventionally, the preliminary design for these steps is obtained using higher order analytical solution and the dynamical systems theory respectively. Refinements of the design are carried out using gradient based methods such as differential correction and pseudo arc length continuation method under the of circular restricted three body model. In this paper, alternative single level schemes are developed for both of these steps based on differential evolution, an evolutionary optimization technique. The differential evolution based scheme for halo orbit design produces precise halo orbit design avoiding the refinement steps. Further, in this approach, prior knowledge of higher order analytical solutions for the halo orbit design is not needed. The differential evolution based scheme for the transfer trajectory, identifies the precise location on the halo orbit that needs minimum energy for insertion and avoids exploration of multiple points. The need of a close guess is removed because the present scheme operates on a set of bounds for the unknowns. The constraint on the closest approach altitude from Earth is handled through objective function. The use of these schemes as the design and analysis tools within the of circular restricted three body model is demonstrated through case studies for missions to the first libration point of Sun-Earth system.

  8. Reversible Sterilization

    ERIC Educational Resources Information Center

    Largey, Gale

    1977-01-01

    Notes that difficult questions arise concerning the use of sterilization for alleged eugenic and euthenic purposes. Thus, how reversible sterilization will be used with relation to the poor, mentally ill, mentally retarded, criminals, and minors, is questioned. (Author/AM)

  9. Reversible Sterilization

    ERIC Educational Resources Information Center

    Largey, Gale

    1977-01-01

    Notes that difficult questions arise concerning the use of sterilization for alleged eugenic and euthenic purposes. Thus, how reversible sterilization will be used with relation to the poor, mentally ill, mentally retarded, criminals, and minors, is questioned. (Author/AM)

  10. Eponymous signs in dermatology

    PubMed Central

    Madke, Bhushan; Nayak, Chitra

    2012-01-01

    Clinical signs reflect the sheer and close observatory quality of an astute physician. Many new dermatological signs both in clinical and diagnostic aspects of various dermatoses are being reported and no single book on dermatology literature gives a comprehensive list of these “signs” and postgraduate students in dermatology finds it difficult to have access to the description, as most of these resident doctor do not have access to the said journal articles. “Signs” commonly found in dermatologic literature with a brief discussion and explanation is reviewed in this paper. PMID:23189246

  11. Solar powered highway sign

    NASA Astrophysics Data System (ADS)

    Hayden, R. L.; Hutter, W.

    1980-09-01

    A roadside sign was equipped with lights powered by photovoltaic solar panels to improve nighttime visibility and evaluate equipment performance and needs. The photovoltaic panels were found to be reliable and effective for powering flashing lights on a highway warning sign. Cost of the panels is high so their use should be limited to locations where commercial electrical power is not available. Solar electric systems should be carefully designed to minimize costs and produce a reliable system. Sufficient prediction for the solar panels should be provided in areas where theft or vandalism might be a problem.

  12. Reversible Cardiomyopathies

    PubMed Central

    Patel, Harsh; Madanieh, Raef; Kosmas, Constantine E; Vatti, Satya K; Vittorio, Timothy J

    2015-01-01

    Cardiomyopathies (CMs) have many etiological factors that can result in severe structural and functional dysregulation. Fortunately, there are several potentially reversible CMs that are known to improve when the root etiological factor is addressed. In this article, we discuss several of these reversible CMs, including tachycardia-induced, peripartum, inflammatory, hyperthyroidism, Takotsubo, and chronic illness–induced CMs. Our discussion also includes a review on their respective pathophysiology, as well as possible management solutions. PMID:26052233

  13. Signs in Speare's "The Sign of the Beaver."

    ERIC Educational Resources Information Center

    Moseley, Ann

    1995-01-01

    Describes the use of signs in Elizabeth George Speare's "The Sign of the Beaver," in which a settler youth and a young Indian learn to communicate by signs, and how the signs reveal much about each character's culture. Summarizes the plot elements of the book, including characters who are not as sympathetic to the Indian point of view.…

  14. Deformed halo nuclei probed by breakup reactions

    NASA Astrophysics Data System (ADS)

    Nakamura, Takashi

    2013-07-01

    Breakup reactions play important roles in elucidating the structures near the drip lines, such as nuclear halo. The recent experimental results using the Coulomb and nuclear breakup reactions for the neutron-drip-line nuclei at the new-generation RI beam facility, RIBF at RIKEN, are presented. Focuses are put on the results on the newly found halo nucleus 31Ne, which is intriguing also in that this nucleus is in the island-of-inversion and thus could be strongly deformed. The results on other Ne/Mg/Si neutron rich isotopes ranging from N=20 towards N=28 are also briefly reported. The first breakup experiments using SAMURAI facility at RIBF and future perspectives are also presented.

  15. Cool Carbon Stars in the Galactic Halo

    NASA Astrophysics Data System (ADS)

    Gigoyan, K. S.

    2016-06-01

    In this paper we report current status of search and study for Faint High Latitude Carbon Stars (FHLCs). Data for more than 1800 spectroscopically confirmed FHLCs are known, which are found thanks to objective prism surveys and photometric selections. More than half of the detected objects belongs to group of dwarf Carbon (dC) stars. Many-sided investigations based on modern astrophysical databases are necessary to study the space distribution of different groups of the FHLC stars and their possible origin in the Halo of our Galaxy. We report about the selection of FHLCs by the spectroscopic surveys: First Byurakan Survey (FBS), Hamburg/ESO Survey (HES), LAMOST Pilot Survey and SDSS, as well as by photometric selection: APM Survey for Cool Carbon Stars in the Galactic Halo, SDSS and 2MASS JHK colours.

  16. Dark-Matter Halos of Tenuous Galaxies

    NASA Astrophysics Data System (ADS)

    Kohler, Susanna

    2016-03-01

    A series of recent deep-imaging surveys has revealed dozens of lurking ultra-diffuse galaxies (UDGs) in nearby galaxy clusters. A new study provides key information to help us understand the origins of these faint giants.What are UDGs?There are three main possibilities for how UDGs galaxies with the sizes of giants, but luminosities no brighter than those of dwarfs formed:They are tidal dwarfs, created in galactic collisions when streams of matter were pulled away from the parent galaxies and halos to form dwarfs.They are descended from normal galaxies and were then altered by tidal interactions with the galaxy cluster.They are ancient remnant systems large galaxies whose gas was swept away, putting an early halt to star formation. The gas removal did not, however, affect their large dark matter halos, which permitted them to survive in the cluster environment.The key to differentiating between these options is to obtain mass measurements for the UDGs how large are their dark matter halos? In a recent study led by Michael Beasley (Institute of Astrophysics of the Canary Islands, University of La Laguna), a team of astronomers has determined a clever approach for measuring these galaxies masses: examine their globular clusters.Masses from Globular ClustersVCC 1287s mass measurements put it outside of the usual halo-mass vs. stellar-mass relationships for nearby galaxies: it has a significantly higher halo mass than is normal, given its stellar mass. [Adapted from Beasley et al. 2016]Beasley and collaborators selected one UDG, VCC 1287, from the Virgo galaxy cluster, and they obtained spectra of the globular clusters around it using the OSIRIS spectrograph on the Great Canary Telescope. They then determined VCC 1287s total halo mass in two ways: first by using the dynamics of the globular clusters, and then by relying on a relation between total globular cluster mass and halo mass.The two masses they found are in good agreement with each other; both are around 80

  17. Probing satellite haloes with weak gravitational lensing

    NASA Astrophysics Data System (ADS)

    Gillis, Bryan R.; Hudson, Michael J.; Hilbert, Stefan; Hartlap, Jan

    2013-02-01

    We demonstrate the possibility of detecting tidal stripping of dark matter subhaloes within galaxy groups using weak gravitational lensing. We have run ray-tracing simulations on galaxy catalogues from the Millennium Simulation to generate mock shape catalogues. The ray-tracing catalogues assume a halo model for galaxies and groups using various models with different distributions of mass between galaxy and group haloes to simulate different stages of group evolution. Using these mock catalogues, we forecast the lensing signals that will be detected around galaxy groups and satellite galaxies, as well as test two different methods for isolating the satellites' lensing signals. A key challenge is to determine the accuracy to which group centres can be identified. We show that with current and ongoing surveys, it will possible to detect stripping in groups of mass 1012-1015 M⊙.

  18. Stellar halos around Local Group galaxies

    NASA Astrophysics Data System (ADS)

    McConnachie, Alan W.

    2016-08-01

    The Local Group is now home to 102 known galaxies and candidates, with many new faint galaxies continuing to be discovered. The total stellar mass range spanned by this population covers a factor of close to a billion, from the faintest systems with stellar masses of order a few thousand to the Milky Way and Andromeda, with stellar masses of order 1011 M ⊙. Here, I discuss the evidence for stellar halos surrounding Local Group galaxies spanning from dwarf scales (with the case of the Andromeda II dwarf spheroidal), though to intermediate mass systems (M33) and finishing with M31. Evidence of extended stellar populations and merging is seen across the luminosity function, indicating that the processes that lead to halo formation are common at all mass scales.

  19. Accurate mass and velocity functions of dark matter haloes

    NASA Astrophysics Data System (ADS)

    Comparat, Johan; Prada, Francisco; Yepes, Gustavo; Klypin, Anatoly

    2017-08-01

    N-body cosmological simulations are an essential tool to understand the observed distribution of galaxies. We use the MultiDark simulation suite, run with the Planck cosmological parameters, to revisit the mass and velocity functions. At redshift z = 0, the simulations cover four orders of magnitude in halo mass from ˜1011M⊙ with 8783 874 distinct haloes and 532 533 subhaloes. The total volume used is ˜515 Gpc3, more than eight times larger than in previous studies. We measure and model the halo mass function, its covariance matrix w.r.t halo mass and the large-scale halo bias. With the formalism of the excursion-set mass function, we explicit the tight interconnection between the covariance matrix, bias and halo mass function. We obtain a very accurate (<2 per cent level) model of the distinct halo mass function. We also model the subhalo mass function and its relation to the distinct halo mass function. The set of models obtained provides a complete and precise framework for the description of haloes in the concordance Planck cosmology. Finally, we provide precise analytical fits of the Vmax maximum velocity function up to redshift z < 2.3 to push for the development of halo occupation distribution using Vmax. The data and the analysis code are made publicly available in the Skies and Universes data base.

  20. A Ly{alpha} HALO AROUND A QUASAR AT REDSHIFT z = 6.4

    SciTech Connect

    Willott, Chris J.; Chet, Savironi; Hutchings, John B.; Bergeron, Jacqueline

    2011-12-15

    We present long-slit spectroscopic data that reveal extended Ly{alpha} emission around the z = 6.417 radio-quiet quasar CFHQS J2329-0301. The Ly{alpha} emission is extended over 15 kpc and has a luminosity of >8 Multiplication-Sign 10{sup 36} W, comparable to the most luminous Ly{alpha} halos known. The emission has complex kinematics, in part due to foreground absorption, which only partly covers the extended nebula. The velocity ranges from -500 km s{sup -1} to +500 km s{sup -1}, with a peak remarkably close to the systemic velocity identified by broad Mg II emission of the quasar. There is no evidence for infall or outflow of the halo gas. We speculate that the Ly{alpha} emission mechanism is recombination after quasar photoionization of gas sitting within a high-mass dark matter halo. The immense Ly{alpha} luminosity indicates a higher covering factor of cold gas compared with typical radio-quiet quasars at lower redshift.

  1. Is the Milky Way's hot halo convectively unstable?

    SciTech Connect

    Henley, David B.; Shelton, Robin L.

    2014-03-20

    We investigate the convective stability of two popular types of model of the gas distribution in the hot Galactic halo. We first consider models in which the halo density and temperature decrease exponentially with height above the disk. These halo models were created to account for the fact that, on some sight lines, the halo's X-ray emission lines and absorption lines yield different temperatures, implying that the halo is non-isothermal. We show that the hot gas in these exponential models is convectively unstable if γ < 3/2, where γ is the ratio of the temperature and density scale heights. Using published measurements of γ and its uncertainty, we use Bayes' theorem to infer posterior probability distributions for γ, and hence the probability that the halo is convectively unstable for different sight lines. We find that, if these exponential models are good descriptions of the hot halo gas, at least in the first few kiloparsecs from the plane, the hot halo is reasonably likely to be convectively unstable on two of the three sight lines for which scale height information is available. We also consider more extended models of the halo. While isothermal halo models are convectively stable if the density decreases with distance from the Galaxy, a model of an extended adiabatic halo in hydrostatic equilibrium with the Galaxy's dark matter is on the boundary between stability and instability. However, we find that radiative cooling may perturb this model in the direction of convective instability. If the Galactic halo is indeed convectively unstable, this would argue in favor of supernova activity in the Galactic disk contributing to the heating of the hot halo gas.

  2. Halo naevi with associated vitiligo-like depigmentations: pathogenetic hypothesis.

    PubMed

    van Geel, N; Speeckaert, R; Lambert, J; Mollet, I; De Keyser, S; De Schepper, S; Brochez, L

    2012-06-01

      In analogy with melanoma-associated leucoderma, halo naevi may trigger in some patients the development of additional depigmentations which are in distribution, extent and prognosis not in accordance with classic vitiligo.   The aim of this study was to support the hypothesis that in a subset of halo naevi patients vitiligo-like lesions develop directly linked to the halo phenomenon.   Forty-one patients with halo naevi were examined for the development of depigmentations not corresponding to typical vitiligo lesions.   We identified a subset of five halo naevi patients with additional subtle depigmentations. After the occurrence of multiple halo naevi, they developed leucoderma that showed a different disease pattern than vitiligo (variable asymmetric distribution, limited extent and lack of progression). Moreover, the characteristics of these halo naevi patients with associated leucoderma were different from classic vitiligo patients (high number of halo naevi, absence of family history for vitiligo and absence of autoimmune diseases) and the timing of occurrence of the leucoderma suggested a direct relation with the halo phenomenon.   In this article, we describe in a limited subset of patients with multiple halo naevi discrete depigmentations at distance from halo naevi which may result from a temporary autoimmune process directly linked to the halo phenomenon. This finding illustrates the collateral damage resulting from skin immunosurveillance and may have clinical consequences as the evolution pattern in this subset of patients is less progressive compared with vitiligo. We present clinical data that support this hypothesis and suggest to call it 'halo naevi-associated leucoderma'. © 2011 The Authors. Journal of the European Academy of Dermatology and Venereology © 2011 European Academy of Dermatology and Venereology.

  3. Prognostic value and clinical significance of halo naevi regarding vitiligo.

    PubMed

    van Geel, N; Vandenhaute, S; Speeckaert, R; Brochez, L; Mollet, I; De Cooman, L; Lambert, J

    2011-04-01

    Vitiligo and halo naevi can present together or separately. Whether they are different entities remains unclear. To assess the clinical significance of halo naevi, both with respect to the future development of vitiligo, and to the clinical profile and course of vitiligo. In total, 291 patients were included in this study: patients with only halo naevi (group 1; n=40), patients with generalized vitiligo without halo naevi (group 2; n=173) and patients with generalized vitiligo with halo naevi (group 3; n=78). Patients with only halo naevi (group 1) reported significantly less associated autoimmune disease (P=0·001), were less likely to have a family history of vitiligo (P=0·013) and were less likely to have presence of Koebner phenomenon (P<0·001) compared with patients with generalized vitiligo (groups 2+3). Multiple halo naevi (≥3) were significantly more frequently observed (P=0·002) in patients from group 1 compared with patients from group 3. In group 3, halo naevi were reported prior to the development of vitiligo in 61% (mean±SD time interval of 33·7±5·17months). No significant correlation was observed between the presence of halo naevi and the extent, activity or subtype of vitiligo. However, halo naevi in patients with vitiligo significantly reduced the risk for associated autoimmune diseases, and age at onset of vitiligo was significantly lower compared with patients with vitiligo without halo naevi (P<0·001). Our results support the hypothesis that halo naevi can represent a distinct condition. In a subset of patients, the occurrence of halo naevi may be an initiating factor in the pathogenesis of vitiligo. © 2011 The Authors. BJD © 2011 British Association of Dermatologists.

  4. Dynamic Colloidal Stabilization by Nanoparticle Halos

    NASA Astrophysics Data System (ADS)

    Karanikas, S.; Louis, A. A.

    2004-12-01

    We explore the conditions under which colloids can be stabilized by the addition of smaller particles. The largest repulsive barriers between colloids occur when the added particles repel each other with soft interactions, leading to an accumulation near the colloid surfaces. At lower densities these layers of mobile particles (nanoparticle halos) result in stabilization, but when too many are added, the interactions become attractive again. We systematically study these effects—accumulation repulsion, reentrant attraction, and bridging—by accurate integral equation techniques.

  5. Stellar Spirals in Triaxial Dark Matter Halos

    NASA Astrophysics Data System (ADS)

    Hu, Shaoran; Sijacki, Debora

    2017-03-01

    Two-armed grand-design spirals may form if the shape of its dark matter halo changes abruptly enough. The feasibility of such a mechanism is tested in realistic simulations. The interplay of such externally-driven spirals and self-induced transient spirals is then studied. Subhaloes are also found to lead to transient grand-design spiral structures when they impact the disk.

  6. Splashback Shells of Cold Dark Matter Halos

    NASA Astrophysics Data System (ADS)

    Mansfield, Philip; Kravtsov, Andrey V.; Diemer, Benedikt

    2017-05-01

    The density field in the outskirts of dark matter halos is discontinuous as a result of a caustic formed by matter at its first apocenter after infall. In this paper, we present an algorithm to identify the “splashback shell” formed by these apocenters in individual simulated halos using only a single snapshot of the density field. We implement this algorithm in the code Shellfish (SHELL Finding In Spheroidal Halos) and demonstrate that the code identifies splashback shells correctly and measures their properties with an accuracy of < 5 % for halos with more than 50,000 particles and mass accretion rates of {{{Γ }}}{DK14}> 0.5. Using Shellfish, we present the first estimates for several basic properties of individual splashback shells, such as radius, {R}{sp}, mass, and overdensity, and provide fits to the distribution of these quantities as functions of {{{Γ }}}{DK14}, {ν }200{{m}}, and z. We confirm previous findings that {R}{sp} decreases with increasing {{{Γ }}}{DK14}, but we show that, independent of accretion rate, it also decreases with increasing {ν }200{{m}}. We also study the 3D structures of these shells and find that they generally have non-ellipsoidal oval shapes. We find that splashback radii estimated by Shellfish are 20%-30% larger than those estimated in previous studies from stacked density profiles at high accretion rates. We demonstrate that the latter are biased low owing to the contribution of high-mass subhalos to these profiles, and we show that using the median instead of mean density in each radial bin mitigates the effect of substructure on density profiles and removes the bias.

  7. The Halo B2B Studio

    NASA Astrophysics Data System (ADS)

    Gorzynski, Mark; Derocher, Mike; Mitchell, April Slayden

    Research underway at Hewlett-Packard on remote communication resulted in the identification of three important components typically missing in existing systems. These missing components are: group nonverbal communication capabilities, high-resolution interactive data capabilities, and global services. Here we discuss some of the design elements in these three areas as part of the Halo program at HP, a remote communication system shown to be effective to end-users.

  8. The Vertical Structure of the Halo Rotation

    NASA Astrophysics Data System (ADS)

    Kinman, T. D.; Bragaglia, A.; Cacciari, C.; Buzzoni, A.; Spagna, A.

    New GSC-II proper motions and radial velocities of RR Lyrae and Blue Horizontal Branch stars near the North Galactic Pole are used to show that the Galactic Halo 5 kpc above the Plane has a significantly retrograde galactic rotation. Streaming motions cannot be excluded. Based on observations collected at the Kitt Peak and TNG Observatories. Funded by MIUR-Cofin 2001 (PI: Gratton).

  9. Sign Language Web Pages

    ERIC Educational Resources Information Center

    Fels, Deborah I.; Richards, Jan; Hardman, Jim; Lee, Daniel G.

    2006-01-01

    The World Wide Web has changed the way people interact. It has also become an important equalizer of information access for many social sectors. However, for many people, including some sign language users, Web accessing can be difficult. For some, it not only presents another barrier to overcome but has left them without cultural equality. The…

  10. Signing in Science

    ERIC Educational Resources Information Center

    Ashby, Rachael

    2013-01-01

    This article describes British Sign Language (BSL) as a viable option for teaching science. BSL is used by a vast number of people in Britain but is seldom taught in schools or included informally alongside lessons. With its new addition of a large scientific glossary, invented to modernise the way science is taught to deaf children, BSL breaks…

  11. Derivative Sign Patterns

    ERIC Educational Resources Information Center

    Clark, Jeffrey

    2011-01-01

    Analysis of the patterns of signs of infinitely differentiable real functions shows that only four patterns are possible if the function is required to exhibit the pattern at all points in its domain and that domain is the set of all real numbers. On the other hand all patterns are possible if the domain is a bounded open interval.

  12. Derivative Sign Patterns

    ERIC Educational Resources Information Center

    Clark, Jeffrey

    2011-01-01

    Analysis of the patterns of signs of infinitely differentiable real functions shows that only four patterns are possible if the function is required to exhibit the pattern at all points in its domain and that domain is the set of all real numbers. On the other hand all patterns are possible if the domain is a bounded open interval.

  13. Buffer Zone Sign Template

    EPA Pesticide Factsheets

    The certified pesticide applicator is required to post a comparable sign, designating a buffer zone around the soil fumigant application block in order to control exposure risk. It must include the don't walk symbol, product name, and applicator contact.

  14. Sign-away Pressures

    ERIC Educational Resources Information Center

    Rosen, Catherine E.

    1976-01-01

    Why would mental health clients sign release-of-information forms unless they thought a refusal to do so would jeopardize their access to service? The author believes that the practice of not advising clients of their rights to privacy has ethical implications that can compromise the value of the treatment. (Author)

  15. Signing in Science

    ERIC Educational Resources Information Center

    Ashby, Rachael

    2013-01-01

    This article describes British Sign Language (BSL) as a viable option for teaching science. BSL is used by a vast number of people in Britain but is seldom taught in schools or included informally alongside lessons. With its new addition of a large scientific glossary, invented to modernise the way science is taught to deaf children, BSL breaks…

  16. Oxygen vs. Age in Halo Field Stars

    NASA Astrophysics Data System (ADS)

    Laird, J. B.; Sneden, C.

    1996-04-01

    Oxygen abundances as a function of age are presented for a sample of halo field stars near the main sequence turn-off. We have measured oxygen abundances using the infrared oxygen triplet, and ages have previously been determined for these stars by Schuster & Nissen and Marquez & Schuster using Stromgren photometry and theoretical isochrones. The age spread observed among globular clusters and among the field stars indicates that the formation of the halo occurred over at least several billion years. The relatively shorter time scale for the contribution of Type Ia supernovae should have produced a significant decrease in the oxygen-to-iron (O/Fe) ratio over this time, leading to a significant variation in [O/Fe] among stars with different ages. We do not find the expected correlation of O/Fe and age. This result suggests that either the timescale for Type Ia supernovae is significantly longer than 1 Gyr or the stars of different ages formed in chemically isolated regions of the halo.

  17. Effects of arm truncation on the appearance of the halo artifact in (68)Ga-PSMA-11 (HBED-CC) PET/MRI.

    PubMed

    Afshar-Oromieh, Ali; Wolf, Maya; Haberkorn, Uwe; Kachelrieß, Marc; Gnirs, Regula; Kopka, Klaus; Schlemmer, Heinz-Peter; Freitag, Martin T

    2017-09-01

    PSMA ligand imaging with hybrid PET/MRI scanners could be an integral part of the clinical routine in the future. However, the first study about this novel method revealed a severe photopenic artifact ("halo artifact") around the urinary bladder causing significantly reduced tumor visibility. The aim of this evaluation was to analyze the role of arm truncation on the appearance of the halo artifact in (68)Ga-PSMA-11 PET/MRI hypothesizing that this influences the appearance. Twenty-seven consecutive patients were subjected to (68)Ga-PSMA-11 PET/CT (1 h p.i.) followed by PET/MRI (3 h p.i.). PET/MRI was first started with scans of the abdomen to pelvis with arms positioned up above the head. Immediately thereafter, additional scans from the pelvis to abdomen were conducted with arms positioned down beside the trunk. All investigations were first analyzed separately and then compared with respect to tumor detection and tumor uptake (SUV) as well as the presence and intensity of the halo artifact. The Wilcoxon signed rank test was used to determine statistical differences including Bonferroni correction. The halo was significantly reduced if the arms were elevated. Lesions inside the halo artifact (n = 16) demonstrated significantly increased SUVmean (p = 0.0007) and SUVmax (p = 0.0024) with arms positioned up. The halo appearance and intensity was not dependent on the total activity and activity concentration of the urinary bladder. Positioning the arms down was shown to be significantly associated with the appearance of the halo artifact in PET/MRI. Positioning the arms up above the head can significantly reduce the halo artifact, thereby detecting more tumor lesions.

  18. The Halo of NGC 2438 scrutinized

    NASA Astrophysics Data System (ADS)

    Oettl, Silvia; Kimeswenger, Stefan

    2015-08-01

    Haloes and multiple shells around planetary nebulae trace the mass-loss history of the central star. The haloes provide us with information about abundances, ionization or kinematics. Detailed investigations of these haloes can be used to study the evolution of the old stellar population in our galaxy and beyond.Different observations show structures in the haloes like radial rays, blisters and rings (e.g., Ramos-Larios et al. 2012, MNRAS 423, 3753 or Matsuura et al. 2009, ApJ, 700, 1067). The origin of these features has been associated with ionization shadows (Balick 2004, AJ, 127, 2262). They can be observed in regions, where dense knots are opaque to stellar ionizing photons. In this regions we can see leaking UV photons.In this work, we present a detailed investigation of the multiple shell PN NGC 2438. We derive a complete data set of the main nebula. This allows us to analize the physical conditions from photoionization models, such as temperature, density and ionization, and clumping.Data from ESO (3.6m telescope - EFOSC1 - direct imaging and long slit spectroscopy) and from SAAO (spectroscopic observations using a small slit) were available. These data were supplemented by imaging data from the HST archive and by archival VLA observations. The low-excitation species are found to be dominated by clumps. The emission line ratios show no evidence for shocks. We find the shell in ionization equilibrium: a significant amount of UV radiation infiltrates the inner nebula. Thus the shell still seems to be ionized.The photoionization code CLOUDY was used to model the nebular properties and to derive a more accurate distance and ionized mass. The model supports the hypothesis that photoionization is the dominant process in this nebula, far out into the shell.If we want to use extragalactic planetary nebulae as probes of the old stellar population, we need to assess the potential impact of a halo on the evolution. Also the connection of observations and models must

  19. Revisiting the Bulge-Halo Conspiracy. I. Dependence on Galaxy Properties and Halo Mass

    NASA Astrophysics Data System (ADS)

    Shankar, Francesco; Sonnenfeld, Alessandro; Mamon, Gary A.; Chae, Kyu-Hyun; Gavazzi, Raphael; Treu, Tommaso; Diemer, Benedikt; Nipoti, Carlo; Buchan, Stewart; Bernardi, Mariangela; Sheth, Ravi; Huertas-Company, Marc

    2017-05-01

    We carry out a systematic investigation of the total mass density profile of massive ({log} {M}{star}/{M}⊙ ≳ 11.3) early-type galaxies and its dependence on galactic properties and host halo mass with the aid of a variety of lensing/dynamical data and large mock galaxy catalogs. The latter are produced via semi-empirical models that, by design, are based on just a few basic input assumptions. Galaxies with measured stellar masses, effective radii, and Sérsic indices, are assigned, via abundance matching relations, host dark matter halos characterized by a typical ΛCDM profile. Our main results are as follows. (1) In line with observational evidence, our semi-empirical models naturally predict that the total, mass-weighted density slope at the effective radius γ‧ is not universal, steepening for more compact and/or massive galaxies, but flattening with increasing host halo mass. (2) Models characterized by a Salpeter or variable initial mass function (IMF) and uncontracted dark matter profiles are in good agreement with the data, while a Chabrier IMF and/or adiabatic contractions/expansions of the dark matter halos are highly disfavored. (3) Currently available data on the mass density profiles of very massive galaxies ({log} {M}{star}/{M}⊙ ≳ 12), with {M}{halo}≳ 3× {10}14 {M}⊙ , favor instead models with a stellar profile flatter than a Sérsic one in the very inner regions (r ≲ 3-5 kpc), and a cored NFW or Einasto dark matter profile with median halo concentration a factor of ˜2 or ≲1.3, respectively, higher than those typically predicted by N-body numerical simulations.

  20. Wrong Signs in Regression Coefficients

    NASA Technical Reports Server (NTRS)

    McGee, Holly

    1999-01-01

    When using parametric cost estimation, it is important to note the possibility of the regression coefficients having the wrong sign. A wrong sign is defined as a sign on the regression coefficient opposite to the researcher's intuition and experience. Some possible causes for the wrong sign discussed in this paper are a small range of x's, leverage points, missing variables, multicollinearity, and computational error. Additionally, techniques for determining the cause of the wrong sign are given.

  1. Wrong Signs in Regression Coefficients

    NASA Technical Reports Server (NTRS)

    McGee, Holly

    1999-01-01

    When using parametric cost estimation, it is important to note the possibility of the regression coefficients having the wrong sign. A wrong sign is defined as a sign on the regression coefficient opposite to the researcher's intuition and experience. Some possible causes for the wrong sign discussed in this paper are a small range of x's, leverage points, missing variables, multicollinearity, and computational error. Additionally, techniques for determining the cause of the wrong sign are given.

  2. Ergonomic guidelines for traffic sign design increase sign comprehension.

    PubMed

    Ben-Bassat, Tamar; Shinar, David

    2006-01-01

    This research directly tests the relationship between comprehension probability of highway signs and the extent to which they comply with three ergonomic principles of design: sign-content compatibility, familiarity, and standardization. A recent study that evaluated comprehension of traffic signs in four different countries showed that comprehension level varies widely and is apparently related to the extent that the sign's design incorporates ergonomic guidelines for good design (D. Shinar, R. E. Dewar, H. Summala, and L. Zakowska 2003). Participants were presented with 30 signs and asked to describe each sign's meaning. They then evaluated each sign in terms of each of three ergonomic principles. In addition, a group of human factors/ergonomics experts evaluated each sign on its standardization and compatibility. There were high correlations between the ratings of the students and the ratings of the experts on compatibility (rho = .94) and on standardization (rho = .84), validating the use of the students' evaluations of the signs on these variables. There was a great variability in signs' comprehension and high and statistically significant correlations between the comprehension level of each sign and the extent to which it complied with compatibility (R = .76), familiarity (R = .89), and standardization (R = .88) principles. The more signs conform to universal ergonomic principles of good design, the more likely they are to be comprehended by drivers of different cultural backgrounds. Sign design should be guided by established ergonomics principles to enhance comprehension, especially for drivers who have not had any prior encounters with specific signs.

  3. Data-Parallel Halo Finder Operator in PISTON

    SciTech Connect

    Widanagamaachchi, W. N.

    2012-08-01

    PISTON is a portable framework which supports the development of visualization and analysis operators using a platform-independent, data-parallel programming model. Operators such as isosurface, cut-surface and threshold have been implemented in this framework, with the exact same operator code achieving good parallel performance on different architectures. An important analysis operator in cosmology is the halo finder. A halo is a cluster of particles and is considered a common feature of interest found in cosmology data. As the number of cosmological simulations carried out in the recent past has increased, the resultant data of these simulations and the required analysis tasks have increased as well. As a consequence, there is a need to develop scalable and efficient tools to carry out the needed analysis. Therefore, we are currently implementing a halo finder operator using PISTON. Researchers have developed a wide variety of techniques to identify halos in raw particle data. The most basic algorithm is the friend-of-friends (FOF) halo finder, where the particles are clustered based on two parameters: linking length and halo size. In a FOF halo finder, all particles which lie within the linking length are considered as one halo and the halos are filtered based on the halo size parameter. A naive implementation of a FOF halo finder compares each and every particle pair, requiring O(n{sup 2}) operations. Our data-parallel halo finder operator uses a balanced k-d tree to reduce this number of operations in the average case, and implements the algorithm using only the data-parallel primitives in order to achieve portability and performance.

  4. Manual Signing in Adults with Intellectual Disability: Influence of Sign Characteristics on Functional Sign Vocabulary

    ERIC Educational Resources Information Center

    Meuris, Kristien; Maes, Bea; De Meyer, Anne-Marie; Zink, Inge

    2014-01-01

    Purpose: The purpose of this study was to investigate the influence of sign characteristics in a key word signing (KWS) system on the functional use of those signs by adults with intellectual disability (ID). Method: All 507 signs from a Flemish KWS system were characterized in terms of phonological, iconic, and referential characteristics.…

  5. Manual Signing in Adults with Intellectual Disability: Influence of Sign Characteristics on Functional Sign Vocabulary

    ERIC Educational Resources Information Center

    Meuris, Kristien; Maes, Bea; De Meyer, Anne-Marie; Zink, Inge

    2014-01-01

    Purpose: The purpose of this study was to investigate the influence of sign characteristics in a key word signing (KWS) system on the functional use of those signs by adults with intellectual disability (ID). Method: All 507 signs from a Flemish KWS system were characterized in terms of phonological, iconic, and referential characteristics.…

  6. Vital signs monitoring system

    NASA Technical Reports Server (NTRS)

    Steffen, Dale A. (Inventor); Sturm, Ronald E. (Inventor); Rinard, George A. (Inventor)

    1981-01-01

    A system is disclosed for monitoring vital physiological signs. Each of the system components utilizes a single hybrid circuit with each component having high accuracy without the necessity of repeated calibration. The system also has low power requirements, provides a digital display, and is of sufficiently small size to be incorporated into a hand-carried case for portable use. Components of the system may also provide independent outputs making the component useful, of itself, for monitoring one or more vital signs. The overall system preferably includes an ECG amplifier and cardiotachometer signal conditioner unit, an impedance pneumograph and respiration rate signal conditioner unit, a heart/breath rate processor unit, a temperature monitoring unit, a selector switch, a clock unit, and an LCD driver unit and associated LCDs, with the system being capable of being expanded as needed or desired, such as, for example, by addition of a systolic/diastolic blood pressure unit.

  7. Expedition 18 Door Signing

    NASA Image and Video Library

    2008-10-11

    Expedition 18 Flight Engineer Yuri V. Lonchakov signs the door of a hotel room at the Cosmonaut Hotel prior to departing for the launch aboard a Soyuz TMA-13 spacecraft, Sunday, Oct. 12, 2008, in Baikonur, Kazakhstan. The Soyuz TMA-13 spacecraft launched from the Baikonur Cosmodrome in Kazakhstan carrying Expedition 18 Commander Michael Fincke, Flight Engineer Yuri V. Lonchakov and American spaceflight participant Richard Garriott. Photo Credit: (NASA/Bill Ingalls)

  8. Expedition 18 Door Signing

    NASA Image and Video Library

    2008-10-11

    Expedition 18 Commander Michael Fincke signs the door of a hotel room at the Cosmonaut Hotel prior to departing for the launch aboard a Soyuz TMA-13 spacecraft, Sunday, Oct. 12, 2008, in Baikonur, Kazakhstan. The Soyuz TMA-13 spacecraft launched from the Baikonur Cosmodrome in Kazakhstan carrying Expedition 18 Commander Michael Fincke, Flight Engineer Yuri V. Lonchakov and American spaceflight participant Richard Garriott. Photo Credit: (NASA/Bill Ingalls)

  9. NASA EPA MOA Signing

    NASA Image and Video Library

    2010-04-25

    NASA Administrator Charles Bolden, left, and U.S. Environmental Protection Agency (EPA) Administrator Lisa P. Jackson, right, sign a Memorandum of Agreement (MOA) to promote collaboration between the two agencies for cooperation in environmental and Earth sciences and environmental management applications as students from the Howard University Middle School of Mathematics and Science look on, Monday, April 26, 2010, at the school in Washington. Photo Credit: (NASA/Paul E. Alers)

  10. NASA EPA MOA Signing

    NASA Image and Video Library

    2010-04-25

    NASA Administrator Charles Bolden, left, and U.S. Environmental Protection Agency (EPA) Administrator Lisa P. Jackson, right, answer questions from students and faculty from the Howard University Middle School of Mathematics and Science after signing a Memorandum of Agreement (MOA) to promote collaboration between the two agencies for cooperation in environmental and Earth sciences and environmental management applications, Monday, April 26, 2010, at the school in Washington. Photo Credit: (NASA/Paul E. Alers)

  11. NASA EPA MOA Signing

    NASA Image and Video Library

    2010-04-25

    NASA Administrator Charles Bolden, foreground, speaks with Howard University students after he and and U.S. Environmental Protection Agency (EPA) Administrator Lisa P. Jackson, right, signed a Memorandum of Agreement (MOA) to promote collaboration between the two agencies for cooperation in environmental and Earth sciences and environmental management applications at the Howard University Middle School of Mathematics and Science, Monday, April 26, 2010, in Washington. Photo Credit: (NASA/Paul E. Alers)

  12. The Integral Sign Galaxy

    NASA Astrophysics Data System (ADS)

    Noll, Keith

    2007-07-01

    We will observe the unusual warped disk galaxy known as the Integral Sign Galaxy, UGC 3697, with a small two-position WFPC2 mosaic. Observations will be obtained in three broad band filters and the resulting image will be released on the 19th anniversary of the launch of the Hubble Space Telescope on ~April 24, 2009. Multidrizzled mosaics will be made available through the archive.

  13. Expedition 37 Door Signing

    NASA Image and Video Library

    2013-09-25

    Expedition 37/38 NASA Flight Engineer Michael Hopkins performs the traditional door signing before he and fellow crewmates, Soyuz Commander Oleg Kotov, Russian Flight Engineer Sergey Ryazanskiy depart the Cosmonaut Hotel for their Soyuz launch to the International Space Station on Wednesday, Sept. 25, 2013, in Baikonur, Kazakhstan. Launch of the Soyuz rocket will send Hopkins, Kotov and Ryazanskiy on a five-month mission aboard the International Space Station. Photo Credit: (NASA/Carla Cioffi)

  14. Expedition 37 Door Signing

    NASA Image and Video Library

    2013-09-25

    Expedition 37/38 Russian Flight Engineer Sergey Ryazanskiy performs the traditional door signing before he and fellow crewmates, Soyuz Commander Oleg Kotov and NASA Flight Engineer Michael Hopkins depart the Cosmonaut Hotel for their Soyuz launch to the International Space Station on Wednesday, Sept. 25, 2013, in Baikonur, Kazakhstan. Launch of the Soyuz rocket will send Hopkins, Kotov and Ryazanskiy on a five-month mission aboard the International Space Station. Photo Credit: (NASA/Carla Cioffi)

  15. Expedition 35 Door Signing

    NASA Image and Video Library

    2013-03-28

    Expedition 35 Soyuz Commander Pavel Vinogradov performs the traditional door signing before he and fellow crewmates, Flight Engineers Chris Cassidy and Alexander Misurkin depart the Cosmonaut Hotel for their Soyuz launch to the International Space Station, Thursday, March 28, 2013, in Baikonur, Kazakhstan. Launch of the Soyuz rocket will send Vinogradov, Cassidy and Misurkin on a five and a half month mission aboard the International Space Station. Photo Credit: (NASA/Carla Cioffi)

  16. Expedition 39 Door Signing

    NASA Image and Video Library

    2014-03-25

    Expedition 39 Flight Engineer Oleg Artemyev, left, of the Russian Federal Space Agency, Roscosmos, performs the traditional door signing at the Cosmonaut hotel as Soyuz Commander Alexander Skvortsov of Roscosmos, looks on, Tuesday, March 25, 2014, in Baikonur, Kazakhstan. Artemyev, Skvortsov, and fellow crew member Flight Engineer Steve Swanson of NASA will launch in their Soyuz TMA-12M spacecraft to the International Space Station to begin a six-month mission. Photo Credit (NASA/Joel Kowsky)

  17. Expedition 35 Door Signing

    NASA Image and Video Library

    2013-03-28

    Expedition 35 NASA Flight Engineer Chris Cassidy performs the traditional door signing before he and fellow crewmates, Soyuz Commander Pavel Vinogradov and Flight Engineer Alexander Misurkin depart the Cosmonaut Hotel for their Soyuz launch to the International Space Station, Thursday, March 28, 2013, in Baikonur, Kazakhstan. Launch of the Soyuz rocket will send Cassidy, Vinogradov and Misurkin on a five and a half month mission aboard the International Space Station. Photo Credit: (NASA/Carla Cioffi)

  18. Expedition 37 Door Signing

    NASA Image and Video Library

    2013-09-25

    Expedition 37/38 Soyuz Commander Oleg Kotov performs the traditional door signing before he and fellow crewmates, NASA Flight Engineer Michael Hopkins, Russian Flight Engineer Sergey Ryazanskiy depart the Cosmonaut Hotel for their Soyuz launch to the International Space Station on Wednesday, Sept. 25, 2013, in Baikonur, Kazakhstan. Launch of the Soyuz rocket will send Hopkins, Kotov and Ryazanskiy on a five-month mission aboard the International Space Station. Photo Credit: (NASA/Carla Cioffi)

  19. Expedition 35 Door Signing

    NASA Image and Video Library

    2013-03-28

    Expedition 35 Russian Flight Engineer Alexander Misurkin performs the traditional door signing before he and fellow crewmates, Soyuz Commander Pavel Vinogradov and NASA Flight Engineer Chris Cassidy depart the Cosmonaut Hotel for their Soyuz launch to the International Space Station, Thursday, March 28, 2013, in Baikonur, Kazakhstan. Launch of the Soyuz rocket will send Misurkin, Vinogradov and Cassidy on a five and a half month mission aboard the International Space Station. Photo Credit: (NASA/Carla Cioffi)

  20. Planetary Vital Signs

    NASA Astrophysics Data System (ADS)

    Kennel, Charles; Briggs, Stephen; Victor, David

    2016-07-01

    The climate is beginning to behave in unusual ways. The global temperature reached unprecedented highs in 2015 and 2016, which led climatologists to predict an enormous El Nino that would cure California's record drought. It did not happen the way they expected. That tells us just how unreliable temperature has become as an indicator of important aspects of climate change. The world needs to go beyond global temperature to a set of planetary vital signs. Politicians should not over focus policy on one indicator. They need to look at the balance of evidence. A coalition of scientists and policy makers should start to develop vital signs at once, since they should be ready at the entry into force of the Paris Agreement in 2020. But vital signs are only the beginning. The world needs to learn how to use the vast knowledge we will be acquiring about climate change and its impacts. Is it not time to use all the tools at hand- observations from space and ground networks; demographic, economic and societal measures; big data statistical techniques; and numerical models-to inform politicians, managers, and the public of the evolving risks of climate change at global, regional, and local scales? Should we not think in advance of an always-on social and information network that provides decision-ready knowledge to those who hold the responsibility to act, wherever they are, at times of their choosing?

  1. The Angular Momentum Distribution within Dark Matter Halos

    NASA Astrophysics Data System (ADS)

    Chen, D.; Jing, Y.

    We study the angular momentum profile of dark matter halos for a statistical sample drawn from a set of high-resolution cosmological simulations of 2563 particles. Two typical Cold Dark Matter (CDM) models have been analyzed, and the halos are selected to have at least 3× 104 particles in order to reliably measure the angular momentum profile. In contrast with the recent claims of Bullock et al. (2001), we find that the degree of misalignment of angular momentum within a halo is very high. About 50 percent of halos have more than 10 percent of halo mass in the mass of negative angular momentum j. After the mass of negative j is excluded, the cumulative mass function M(halos (˜ 50%) which exhibit systematic deviations from the universal function. Our results, however, are broadly in good agreement with the recent work of van den Bosch et al. (2002). We also study the angular momentum profile of halos in a Warm Dark Matter (WDM) model and a Self-Interacting Dark Matter (SIDM) model. We find that the angular momentum profile of halos in the WDM is statistically indistinguishable from that in the CDM model, but the angular momentum of halos in the SIDM is reduced by the self-interaction of dark matter.

  2. Angular Momentum Profiles of Warm Dark Matter Halos

    NASA Astrophysics Data System (ADS)

    Bullock, James S.; Kravtsov, and Andrey V.; Colín, Pedro

    2002-01-01

    We compare the specific angular momentum profiles of virialized dark halos in cold dark matter (CDM) and warm dark matter (WDM) models, using high-resolution dissipationless simulations. The simulations were initialized using the same set of modes, except on small scales, where the power was suppressed in WDM below the filtering length. Remarkably, WDM as well as CDM halos are well described by the two-parameter angular momentum profile of Bullock and coworkers, even though the halo masses are below the filtering scale of the WDM. Although the best-fit shape parameters change quantitatively for individual halos in the two simulations, we find no systematic variation in profile shapes as a function of the dark matter type. The scatter in shape parameters is significantly smaller for the WDM halos, suggesting that substructure and/or merging history plays a role in producing scatter about the mean angular momentum distribution, but that the average angular momentum profiles of halos originate from larger scale phenomena or a mechanism associated with the virialization process. The known mismatch between the angular momentum distributions of dark halos and disk galaxies is, therefore, present in WDM as well as CDM models. Our WDM halos tend to have a less coherent (more misaligned) angular momentum structure and smaller spin parameters than do their CDM counterparts, although we caution that this result is based on a small number of halos.

  3. Two stellar components in the halo of the Milky Way.

    PubMed

    Carollo, Daniela; Beers, Timothy C; Lee, Young Sun; Chiba, Masashi; Norris, John E; Wilhelm, Ronald; Sivarani, Thirupathi; Marsteller, Brian; Munn, Jeffrey A; Bailer-Jones, Coryn A L; Fiorentin, Paola Re; York, Donald G

    2007-12-13

    The halo of the Milky Way provides unique elemental abundance and kinematic information on the first objects to form in the Universe, and this information can be used to tightly constrain models of galaxy formation and evolution. Although the halo was once considered a single component, evidence for its dichotomy has slowly emerged in recent years from inspection of small samples of halo objects. Here we show that the halo is indeed clearly divisible into two broadly overlapping structural components--an inner and an outer halo--that exhibit different spatial density profiles, stellar orbits and stellar metallicities (abundances of elements heavier than helium). The inner halo has a modest net prograde rotation, whereas the outer halo exhibits a net retrograde rotation and a peak metallicity one-third that of the inner halo. These properties indicate that the individual halo components probably formed in fundamentally different ways, through successive dissipational (inner) and dissipationless (outer) mergers and tidal disruption of proto-Galactic clumps.

  4. Squeezing the halo bispectrum: a test of bias models

    NASA Astrophysics Data System (ADS)

    Moradinezhad Dizgah, Azadeh; Chan, Kwan Chuen; Noreña, Jorge; Biagetti, Matteo; Desjacques, Vincent

    2016-09-01

    We study the halo-matter cross bispectrum in the presence of primordial non-Gaussianity of the local type. We restrict ourselves to the squeezed limit, for which the calculation are straightforward, and perform the measurements in the initial conditions of N-body simulations, to mitigate the contamination induced by nonlinear gravitational evolution. Interestingly, the halo-matter cross bispectrum is not trivial even in this simple limit as it is strongly sensitive to the scale-dependence of the quadratic and third-order halo bias. Therefore, it can be used to test biasing prescriptions. We consider three different prescription for halo clustering: excursion set peaks (ESP), local bias and a model in which the halo bias parameters are explicitly derived from a peak-background split. In all cases, the model parameters are fully constrained with statistics other than the cross bispectrum. We measure the cross bispectrum involving one halo fluctuation field and two mass overdensity fields for various halo masses and collapse redshifts. We find that the ESP is in reasonably good agreement with the numerical data, while the other alternatives we consider fail in various cases. This suggests that the scale-dependence of halo bias also is a crucial ingredient to the squeezed limit of the halo bispectrum.

  5. Halo particle confinement in the VLHC using optical stochastic cooling

    SciTech Connect

    Zholents, Alexander; Barletta, W.; Chattopadhyay, S.; Zolotorev, M.

    2000-06-01

    Beam halo particles following the extreme trajectories near the physical aperture limit radiate Smith-Purcell radiation when moving over a diffraction grating. This grating can be used as a pick-up and a kicker for optical stochastic cooling of the halo particles. In this application cooling would have the effect of slowing down the halo particle diffusion onto the aperture. Cooling efficiency would quickly diminish with the distance from the aperture and would only affect the halo particles. A preliminary analysis of this system is considered.

  6. N-body dark matter haloes with simple hierarchical histories

    NASA Astrophysics Data System (ADS)

    Jiang, Lilian; Helly, John C.; Cole, Shaun; Frenk, Carlos S.

    2014-05-01

    We present a new algorithm which groups the subhaloes found in cosmological N-body simulations by structure finders such as SUBFIND into dark matter haloes whose formation histories are strictly hierarchical. One advantage of these `Dhaloes' over the commonly used friends-of-friends (FoF) haloes is that they retain their individual identity in the cases when FoF haloes are artificially merged by tenuous bridges of particles or by an overlap of their outer diffuse haloes. Dhaloes are thus well suited for modelling galaxy formation and their merger trees form the basis of the Durham semi-analytic galaxy formation model, GALFORM. Applying the Dhalo construction to the Λ cold dark matter Millennium II Simulation, we find that approximately 90 per cent of Dhaloes have a one-to-one, bijective match with a corresponding FoF halo. The remaining 10 per cent are typically secondary components of large FoF haloes. Although the mass functions of both types of haloes are similar, the mass of Dhaloes correlates much more tightly with the virial mass, M200, than FoF haloes. Approximately 80 per cent of FoF and bijective and non-bijective Dhaloes are relaxed according to standard criteria. For these relaxed haloes, all three types have similar concentration-M200 relations and, at fixed mass, the concentration distributions are described accurately by log-normal distributions.

  7. Milky Way is Surrounded by Huge Halo of Hot Gas

    NASA Image and Video Library

    2012-09-24

    Astronomers have used Chandra to find evidence that our Milky Way Galaxy is embedded in an enormous halo of hot gas that extends for hundreds of thousands of light years. This artist's illustration shows the halo of hot gas, in blue, around the Milky Way and two small neighboring galaxies. The mass of the halo is estimated to be comparable to the mass of all the stars in the Milky Way galaxy. If the size and mass of this gas halo is confirmed, it could be the solution to the "missing-baryon" problem for the Galaxy.

  8. Light source halos in night vision goggles: psychophysical assessments

    NASA Astrophysics Data System (ADS)

    Craig, Greg; Macuda, Todd; Thomas, Paul; Allison, Rob; Jennings, Sion

    2005-05-01

    Anecdotal reports by pilots flying with Night Vision Goggles (NVGs) in urban environments suggest that halos produced by bright light sources impact flight performance. The current study developed a methodology to examine the impact of viewing distance on perceived halo size. This was a first step in characterizing the subtle phenomenon of halo. Observers provided absolute size estimates of halos generated by a red LED at several viewing distances. Physical measurements of these halos were also recorded. The results indicated that the perceived halo linear size decreased as viewing distance was decreased. Further, the data showed that halos subtended a constant visual angle on the goggles (1°48", +/-7") irrespective of distance up to 75". This invariance with distance may impact pilot visual performance. For example, the counterintuitive apparent contraction of halo size with decreasing viewing distance may impact estimates of closure rates and of the spatial layout of light sources in the scene. Preliminary results suggest that halo is a dynamic phenomenon that requires further research to characterize the specific perceptual effects that it might have on pilot performance.

  9. Effects of image intensifier halo on perceived layout

    NASA Astrophysics Data System (ADS)

    Zacher, James E.; Brandwood, Tracey; Thomas, Paul; Vinnikov, Margarita; Xu, Gancun; Jennings, Sion; Macuda, Todd; Palmisano, Stephan A.; Craig, Greg; Wilcox, Laurie; Allison, Robert S.

    2007-04-01

    Night vision devices (NVDs) or night-vision goggles (NVGs) based on image intensifiers improve nighttime visibility and extend night operations for military and increasingly civil aviation. However, NVG imagery is not equivalent to daytime vision and impaired depth and motion perception has been noted. One potential cause of impaired perceptions of space and environmental layout is NVG halo, where bright light sources appear to be surrounded by a disc-like halo. In this study we measured the characteristics of NVG halo psychophysically and objectively and then evaluated the influence of halo on perceived environmental layout in a simulation experiment. Halos are generated in the device and are not directly related to the spatial layout of the scene. We found that, when visible, halo image (i.e. angular) size was only weakly dependent on both source intensity and distance although halo intensity did vary with effective source intensity. The size of halo images surrounding lights sources are independent of the source distance and thus do not obey the normal laws of perspective. In simulation experiments we investigated the effect of NVG halo on judgements of observer attitude with respect to the ground during simulated flight. We discuss the results in terms of NVG design and of the ability of human operators to compensate for perceptual distortions.

  10. Reversible Computing

    DTIC Science & Technology

    1980-02-01

    will have been introduced. 9. Reversible celular autemata We shall assume the reader to have some familiarity with the concept of cel- lular...10003 Mr. Kin B. Thcmpson 1 copy Technical Director Information Systems Divisia.i Naval Research Laboratory (OP-91T) Technical Information Division

  11. Reverse mortgages.

    PubMed

    Farnesi, D

    1995-09-01

    Elders and their families are often caught in a financial bind when it comes to paying for much-needed home care services. Reverse mortgages may offer a solution to elderly home care clients who own their homes but have a limited income with which to maintain their independence.

  12. REVERSE OSMOSIS,

    DTIC Science & Technology

    acetate membranes. Mechanisms of the process and porous cellulose acetate membrane technology are briefly reviewed. Based on a general capillary...The reverse osmosis process is discussed with particular reference to systems involving aqueous solutions and Loeb-Sourirajan-type porous cellulose

  13. THE SPACE MOTION OF LEO I: THE MASS OF THE MILKY WAY'S DARK MATTER HALO

    SciTech Connect

    Boylan-Kolchin, Michael; Bullock, James S.; Sohn, Sangmo Tony; Van der Marel, Roeland P.; Besla, Gurtina

    2013-05-10

    We combine our Hubble Space Telescope measurement of the proper motion of the Leo I dwarf spheroidal galaxy (presented in a companion paper) with the highest resolution numerical simulations of Galaxy-size dark matter halos in existence to constrain the mass of the Milky Way's dark matter halo (M{sub vir,MW}). Despite Leo I's large Galactocentric space velocity (200 km s{sup -1}) and distance (261 kpc), we show that it is extremely unlikely to be unbound if Galactic satellites are associated with dark matter substructure, as 99.9% of subhalos in the simulations are bound to their host. The observed position and velocity of Leo I strongly disfavor a low-mass Milky Way: if we assume that Leo I is the least bound of the Milky Way's classical satellites, then we find that M{sub vir,MW} > 10{sup 12} M{sub Sun} at 95% confidence for a variety of Bayesian priors on M{sub vir,MW}. In lower mass halos, it is vanishingly rare to find subhalos at 261 kpc moving as fast as Leo I. Should an additional classical satellite be found to be less bound than Leo I, this lower limit on M{sub vir,MW} would increase by 30%. Imposing a mass-weighted {Lambda}CDM prior, we find a median Milky Way virial mass of M{sub vir,MW} = 1.6 Multiplication-Sign 10{sup 12} M{sub Sun }, with a 90% confidence interval of [1.0-2.4] Multiplication-Sign 10{sup 12} M{sub Sun }. We also confirm a strong correlation between subhalo infall time and orbital energy in the simulations and show that proper motions can aid significantly in interpreting the infall times and orbital histories of satellites.

  14. Mapping stellar content to dark matter haloes - II. Halo mass is the main driver of galaxy quenching

    NASA Astrophysics Data System (ADS)

    Zu, Ying; Mandelbaum, Rachel

    2016-04-01

    We develop a simple yet comprehensive method to distinguish the underlying drivers of galaxy quenching, using the clustering and galaxy-galaxy lensing of red and blue galaxies in Sloan Digital Sky Survey. Building on the iHOD framework developed by Zu & Mandelbaum, we consider two quenching scenarios: (1) a `halo' quenching model in which halo mass is the sole driver for turning off star formation in both centrals and satellites; and (2) a `hybrid' quenching model in which the quenched fraction of galaxies depends on their stellar mass, while the satellite quenching has an extra dependence on halo mass. The two best-fitting models describe the red galaxy clustering and lensing equally well, but halo quenching provides significantly better fits to the blue galaxies above 1011 h-2 M⊙. The halo quenching model also correctly predicts the average halo mass of the red and blue centrals, showing excellent agreement with the direct weak lensing measurements of locally brightest galaxies. Models in which quenching is not tied to halo mass, including an age-matching model in which galaxy colour depends on halo age at fixed M*, fail to reproduce the observed halo mass for massive blue centrals. We find similar critical halo masses responsible for the quenching of centrals and satellites (˜1.5 × 1012 h-1 M⊙), hinting at a uniform quenching mechanism for both, e.g. the virial shock heating of infalling gas. The success of the iHOD halo quenching model provides strong evidence that the physical mechanism that quenches star formation in galaxies is tied principally to the masses of their dark matter haloes rather than the properties of their stellar components.

  15. What is the importance of "halo" phenomenon around bone cement following vertebral augmentation for osteoporotic compression fracture?

    PubMed

    Kim, K H; Kuh, S U; Park, J Y; Kim, K S; Chin, D K; Cho, Y E

    2012-10-01

    = 0.002) were significantly associated with peri-cement halo. The peri-cement halo was found to be associated with vertebral recollapse, this sign likely represents a poor prognostic factor after vertebral augmentation for osteoporotic compression fractures.

  16. Levy-Student distributions for halos in accelerator beams

    SciTech Connect

    Cufaro Petroni, Nicola; De Martino, Salvatore; De Siena, Silvio; Illuminati, Fabrizio

    2005-12-15

    We describe the transverse beam distribution in particle accelerators within the controlled, stochastic dynamical scheme of stochastic mechanics (SM) which produces time reversal invariant diffusion processes. This leads to a linearized theory summarized in a Schroedinger-like (SL) equation. The space charge effects have been introduced in recent papers by coupling this S-L equation with the Maxwell equations. We analyze the space-charge effects to understand how the dynamics produces the actual beam distributions, and in particular we show how the stationary, self-consistent solutions are related to the (external and space-charge) potentials both when we suppose that the external field is harmonic (constant focusing), and when we a priori prescribe the shape of the stationary solution. We then proceed to discuss a few other ideas by introducing generalized Student distributions, namely, non-Gaussian, Levy infinitely divisible (but not stable) distributions. We will discuss this idea from two different standpoints: (a) first by supposing that the stationary distribution of our (Wiener powered) SM model is a Student distribution; (b) by supposing that our model is based on a (non-Gaussian) Levy process whose increments are Student distributed. We show that in the case (a) the longer tails of the power decay of the Student laws and in the case (b) the discontinuities of the Levy-Student process can well account for the rare escape of particles from the beam core, and hence for the formation of a halo in intense beams.

  17. 77 FR 75672 - Manufacturer of Controlled Substances, Notice of Registration, Halo Pharmaceutical, Inc.

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-12-21

    ... Enforcement Administration Manufacturer of Controlled Substances, Notice of Registration, Halo Pharmaceutical... 47114, Halo Pharmaceutical, Inc., 30 North Jefferson Road, Whippany, New Jersey 07981, made application... determined that the registration of Halo Pharmaceutical, Inc., to manufacture the listed basic classes...

  18. 77 FR 16264 - Manufacturer of Controlled Substances, Notice of Registration; Halo Pharmaceutical Inc.

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-03-20

    ... Enforcement Administration Manufacturer of Controlled Substances, Notice of Registration; Halo Pharmaceutical... FR 77850, Halo Pharmaceutical Inc., 30 North Jefferson Road, Whippany, New Jersey 07981, made... determined that the registration of Halo Pharmaceutical Inc. to manufacture the listed basic classes...

  19. The accreted stellar halo as a window on halo assembly in L* galaxies

    NASA Astrophysics Data System (ADS)

    Amorisco, Nicola C.

    2017-07-01

    Theory and observations agree that the accreted stellar haloes (ASHs) of Milky Way-like galaxies display significant scatter. I take advantage of this stochasticity to invert the link between halo assembly history (HAH) and ASH, using mock ASHs corresponding to 750 ΛCDM HAHs, sharing a final virial mass of Mh(z = 0) = 1012.25M⊙. Hosts with poor/rich ASHs assemble following orthogonal growth-patterns. Hosts with rich ASHs experience accretion events (AEs) with high virial mass ratios (HVMRs, Ms/Mh ≳ 0.1) at 0.5 ≲ zinfall ≲ 1.5, in a phase of fast growth. This maximizes the accreted stellar mass under the condition these satellites are disrupted by z = 0. At similar times, hosts with poor ASHs grow slowly through minor mergers, with only very recent HVMR AEs: this results in a globally more abundant satellite population and in distinctive surviving massive satellites (stellar mass log Ms, */M⊙ ≳ 9). Several properties of the Milky Way are in agreement with the predictions of this framework for hosts with poor, concentrated ASHs, including: (i) the recent infall of Sagittarius and Magellanic Clouds, (ii) the likely higher-than-average concentration of its dark halo and (iii) the signatures of fast chemical enrichment of a sizable fraction of its halo stellar populations.

  20. Composition of Low-redshift Halo Gas

    NASA Astrophysics Data System (ADS)

    Cen, Renyue

    2013-06-01

    Halo gas in low-z (z < 0.5) >=0.1 L * galaxies in high-resolution, large-scale cosmological hydrodynamic simulations is examined with respect to three components: cold, warm, and hot with temperatures of <105, 105-6, and >106 K, respectively. Utilizing O VI λλ1032, 1038 absorption lines, the warm component is compared to observations, and agreement is found with respect to the galaxy-O VI line correlation, the ratio of the O VI line incidence rate in blue to red galaxies, and the amount of O VI mass in star-forming galaxies. A detailed account of the sources of warm halo gas (stellar feedback heating, gravitational shock heating, and accretion from the intergalactic medium), inflowing and outflowing warm halo gas metallicity disparities, and their dependencies on galaxy types and environment is also presented. With the warm component securely anchored, our simulations make the following additional predictions. First, cold gas is the primary component in inner regions with its mass comprising 50% of all gas within galactocentric radius r = (30, 150) kpc in (red, blue) galaxies. Second, at r > (30, 200) kpc in (red, blue) galaxies the hot component becomes the majority. Third, the warm component is a perpetual minority, with its contribution peaking at ~30% at r = 100-300 kpc in blue galaxies and never exceeding 5% in red galaxies. The significant amount of cold gas in low-z early-type galaxies, which was found in simulations and in agreement with recent observations (Thom et al.), is intriguing, as is the dominance of hot gas at large radii in blue galaxies.

  1. Baryonic distributions in galaxy dark matter halos

    NASA Astrophysics Data System (ADS)

    Richards, Emily E.

    In our best current understanding of the growth of structure in the Universe, visibly complex distributions of gas and stars form and evolve into a wide range of galaxies inside overdensities of dark matter. Re-creating the observed diversity in the organization of baryonic mass within dark matter halos represents a key challenge for galaxy formation models. In this dissertation, I constrain the distribution of baryonic and non-baryonic matter in a statistically representative sample of 44 nearby galaxies defined from the Extended Disk Galaxy Exploration Science (EDGES) survey to address the growth of galaxy disks in dark matter halos. I trace the gravitational potentials of each galaxy using rotation curves derived from new and archival radio synthesis observations of neutral hydrogen (HI). The measured rotation curves are decomposed into baryonic and dark matter halo components using 3.6 mum images for the stellar content, the HI observations for the atomic gas component, and, when available, CO data from the literature for the molecular gas component. The HI kinematics are supplemented with optical integral field spectroscopic (IFS) observations to measure the central ionized gas kinematics in 26 galaxies. Distributions of baryonic-to-total mass ratios are determined from the rotation curve decompositions under different assumptions about the contribution of the stellar component, and are compared to global and radial properties of the dominant stellar populations extracted from optical and near-infrared photometry. Galaxies are grouped into clusters of similar baryonic-to-total mass distributions to examine whether they also exhibit similar star and gas properties. The radial distribution of baryonic-to-total mass in a galaxy does not appear to correlate with any characteristics of its star formation history. This result encapsulates the challenge facing simulations to create galaxies which evolve with different star formation histories but similar

  2. COMPOSITION OF LOW-REDSHIFT HALO GAS

    SciTech Connect

    Cen Renyue

    2013-06-20

    Halo gas in low-z (z < 0.5) {>=}0.1 L{sub *} galaxies in high-resolution, large-scale cosmological hydrodynamic simulations is examined with respect to three components: cold, warm, and hot with temperatures of <10{sup 5}, 10{sup 5-6}, and >10{sup 6} K, respectively. Utilizing O VI {lambda}{lambda}1032, 1038 absorption lines, the warm component is compared to observations, and agreement is found with respect to the galaxy-O VI line correlation, the ratio of the O VI line incidence rate in blue to red galaxies, and the amount of O VI mass in star-forming galaxies. A detailed account of the sources of warm halo gas (stellar feedback heating, gravitational shock heating, and accretion from the intergalactic medium), inflowing and outflowing warm halo gas metallicity disparities, and their dependencies on galaxy types and environment is also presented. With the warm component securely anchored, our simulations make the following additional predictions. First, cold gas is the primary component in inner regions with its mass comprising 50% of all gas within galactocentric radius r = (30, 150) kpc in (red, blue) galaxies. Second, at r > (30, 200) kpc in (red, blue) galaxies the hot component becomes the majority. Third, the warm component is a perpetual minority, with its contribution peaking at {approx}30% at r = 100-300 kpc in blue galaxies and never exceeding 5% in red galaxies. The significant amount of cold gas in low-z early-type galaxies, which was found in simulations and in agreement with recent observations (Thom et al.), is intriguing, as is the dominance of hot gas at large radii in blue galaxies.

  3. Sign language perception research for improving automatic sign language recognition

    NASA Astrophysics Data System (ADS)

    ten Holt, Gineke A.; Arendsen, Jeroen; de Ridder, Huib; Koenderink-van Doorn, Andrea J.; Reinders, Marcel J. T.; Hendriks, Emile A.

    2009-02-01

    Current automatic sign language recognition (ASLR) seldom uses perceptual knowledge about the recognition of sign language. Using such knowledge can improve ASLR because it can give an indication which elements or phases of a sign are important for its meaning. Also, the current generation of data-driven ASLR methods has shortcomings which may not be solvable without the use of knowledge on human sign language processing. Handling variation in the precise execution of signs is an example of such shortcomings: data-driven methods (which include almost all current methods) have difficulty recognizing signs that deviate too much from the examples that were used to train the method. Insight into human sign processing is needed to solve these problems. Perceptual research on sign language can provide such insights. This paper discusses knowledge derived from a set of sign perception experiments, and the application of such knowledge in ASLR. Among the findings are the facts that not all phases and elements of a sign are equally informative, that defining the 'correct' form for a sign is not trivial, and that statistical ASLR methods do not necessarily arrive at sign representations that resemble those of human beings. Apparently, current ASLR methods are quite different from human observers: their method of learning gives them different sign definitions, they regard each moment and element of a sign as equally important and they employ a single definition of 'correct' for all circumstances. If the object is for an ASLR method to handle natural sign language, then the insights from sign perception research must be integrated into ASLR.

  4. The Halo Stars in NGC 5128. III. An Inner Halo Field and the Metallicity Distribution

    NASA Astrophysics Data System (ADS)

    Harris, William E.; Harris, Gretchen L. H.

    2002-06-01

    We present new Hubble Space Telescope WFPC2 (V,I) photometry for field stars in NGC 5128 at a projected distance of 8 kpc from the galaxy center, which probes a mixture of its inner halo and outer bulge. The color-magnitude diagram shows an old red giant branch that is even broader in color than our two previously studied outer halo fields (at 21 and 31 kpc), with significant numbers of stars extending to solar metallicity and higher. The peak frequency of the metallicity distribution function (MDF) is at [m/H]~=-0.4, with even fewer metal-poor stars than in the outer halo fields. If we use the 21 and 31 kpc fields to define template ``halo'' MDFs and subtract these from the 8 kpc field, the residual ``bulge'' population has a mean [m/H]~=-0.2, similar to the bulges of other large spiral and elliptical galaxies. We find that the main features of the halo MDF can be reproduced by a simple chemical evolution model in which early star formation goes on simultaneously with an initial stage of rapid infall of very metal-poor gas, after which the infall dies away exponentially. Finally, by comparison with the MDFs for the NGC 5128 globular clusters, we find that in all the halo fields we have studied there is a clear decrease of specific frequency SN (number of clusters per unit halo light) with increasing metallicity. At the lowest-metallicity range ([Fe/H]<-1.6) SN is ~4-8, while at metallicities [Fe/H]>-1 it has dropped to ~=1.5. This trend may indicate that globular cluster formation efficiency is a strong function of the metallicity of the protocluster gas. However, we suggest an alternate possibility, which is that globular clusters form preferentially sooner than field stars. If most of the cluster formation within a host giant molecular cloud takes place sooner than most of the distributed field-star formation and if the earliest most metal-poor star-forming clouds are prematurely disrupted by their own first bursts of star formation, then they would leave

  5. HOW WELL DO COSMOLOGICAL SIMULATIONS REPRODUCE INDIVIDUAL HALO PROPERTIES?

    SciTech Connect

    Trenti, Michele; Smith, Britton D.; Hallman, Eric J.; Skillman, Samuel W.; Shull, J. Michael

    2010-03-10

    Cosmological simulations of galaxy formation often rely on prescriptions for star formation and feedback that depend on halo properties such as halo mass, central overdensity, and virial temperature. In this paper, we address the convergence of individual halo properties, based on their number of particles N, focusing, in particular, on the mass of halos near the resolution limit of a simulation. While it has been established that the halo mass function is sampled on average down to N {approx} 20-30 particles, we show that individual halo properties exhibit significant scatter, and some systematic biases, as one approaches the resolution limit. We carry out a series of cosmological simulations using the Gadget2 and Enzo codes with N{sub p} = 64{sup 3} to N{sub p} = 1024{sup 3} total particles, keeping the same large-scale structure in the simulation box. We consider boxes of small (l{sub box} = 8 Mpc h {sup -1}), medium (l{sub box} = 64 Mpc h {sup -1}), and large (l{sub box} = 512 Mpc h {sup -1}) size to probe different halo masses and formation redshifts. We cross-identify dark matter halos in boxes at different resolutions and measure the scatter in their properties. The uncertainty in the mass of single halos depends on the number of particles (scaling approximately as N {sup -1/3}), but the rarer the density peak, the more robust its identification. The virial radius of halos is very stable and can be measured without bias for halos with N {approx}> 30. In contrast, the average density within a sphere containing 25% of the total halo mass is severely underestimated (by more than a factor 2) and the halo spin is moderately overestimated for N {approx}< 100. If sub-grid physics is implemented upon a cosmological simulation, we recommend that rare halos ({approx}3sigma peaks) be resolved with N {approx}> 100 particles and common halos ({approx}1sigma peaks) with N {approx}> 400 particles to avoid excessive numerical noise and possible systematic biases in the

  6. Diverse stellar haloes in nearby Milky Way mass disc galaxies

    NASA Astrophysics Data System (ADS)

    Harmsen, Benjamin; Monachesi, Antonela; Bell, Eric F.; de Jong, Roelof S.; Bailin, Jeremy; Radburn-Smith, David J.; Holwerda, Benne W.

    2017-04-01

    We have examined the resolved stellar populations at large galactocentric distances along the minor axis (from 10 kpc up to between 40 and 75 kpc), with limited major axis coverage, of six nearby highly inclined Milky Way (MW) mass disc galaxies using Hubble Space Telescope data from the Galaxy haloes, Outer discs, Substructure, Thick discs, and Star clusters (GHOSTS) survey. We select red giant branch stars to derive stellar halo density profiles. The projected minor axis density profiles can be approximated by power laws with projected slopes of -2 to -3.7 and a diversity of stellar halo masses of 1-6 × 109 M⊙, or 2-14 per cent of the total galaxy stellar masses. The typical intrinsic scatter around a smooth power-law fit is 0.05-0.1 dex owing to substructure. By comparing the minor and major axis profiles, we infer projected axis ratios c/a at ∼25 kpc between 0.4and0.75. The GHOSTS stellar haloes are diverse, lying between the extremes charted out by the (rather atypical) haloes of the MW and M31. We find a strong correlation between the stellar halo metallicities and the stellar halo masses. We compare our results with cosmological models, finding good agreement between our observations and accretion-only models where the stellar haloes are formed by the disruption of dwarf satellites. In particular, the strong observed correlation between stellar halo metallicity and mass is naturally reproduced. Low-resolution hydrodynamical models have unrealistically high stellar halo masses. Current high-resolution hydrodynamical models appear to predict stellar halo masses somewhat higher than observed but with reasonable metallicities, metallicity gradients, and density profiles.

  7. The Prevalence of the 22 deg Halo in Cirrus Clouds

    NASA Technical Reports Server (NTRS)

    Diedenhoven, vanBastiaan

    2014-01-01

    Halos at 22 deg from the sun attributed to randomly-orientated, pristine hexagonal crystals are frequently observed through ice clouds. These frequent sightings of halos formed by pristine crystals pose an apparent inconsistency with the dominance of distorted, nonpristine ice crystals indicated by in situ and remote sensing data. Furthermore, the 46 deg halo, which is associated with pristine hexagonal crystals as well, is observed far less frequently than the 22 deg halo. Considering that plausible mechanisms that could cause crystal distortion such as aggregation, sublimation, riming and collisions are stochastic processes that likely lead to distributions of crystals with varying distortion levels, here the presence of the 22 deg and 46 deg halo features in phase functions of mixtures of pristine and distorted hexagonal ice crystals is examined. We conclude that the 22 deg halo feature is generally present if the contribution by pristine crystals to the total scattering cross section is greater than only about 10% in the case of compact particles or columns, and greater than about 40% for plates. The 46 deg halo feature is present only if the mean distortion level is low and the contribution of pristine crystals to the total scattering cross section is above about 20%, 50% and 70%, in the case of compact crystals, plates and columns, respectively. These results indicate that frequent sightings of 22 deg halos are not inconsistent with the observed dominance of distorted, non-pristine ice crystals. Furthermore, the low mean distortion levels and large contributions by pristine crystals needed to produce the 461 halo features provide a potential explanation of the common sighting of the 22 deg halo without any detectable 46 deg halo.

  8. Asymmetries in the inner regions of ΛCDM haloes

    NASA Astrophysics Data System (ADS)

    Gao, Liang; White, Simon D. M.

    2006-11-01

    Many galaxies display warps, lopsided images, asymmetric rotation curves or other features which suggest that their immediate dynamical environment is neither static nor in equilibrium. In cold dark matter (CDM) theories, such non-equilibrium features are expected in the inner regions of many dark haloes as a result of recent hierarchical growth. We used the excellent statistics provided by the very large Millennium Simulation to study (i) how the distribution of position and velocity asymmetries predicted for halo cores by the concordance ΛCDM cosmogony depends on halo mass and (ii) how much of the dark matter in the inner core has been added at relatively recent times. Asymmetries are typically larger in more massive haloes. Thus 20 per cent of cluster haloes have density centre separated from barycentre by more than 20 per cent of the virial radius, while only 7 per cent of Milky Way haloes have such large asymmetries. About 40 per cent of all cluster haloes have a mean core velocity which differs from the barycentre velocity by more than a quarter of the characteristic halo circular velocity, whereas only 10 per cent of Milky Way haloes have such large velocity offsets. About 25 per cent of all cluster haloes have acquired more than a quarter of the mass currently in their inner 10 kpc through mergers since z = 1. The corresponding percentage of Milky Way haloes is 15 per cent. These numbers seem quite compatible with the levels of asymmetry seen in the observable regions of galaxies, but quantitative comparison requires more detailed modelling of the observable components.

  9. Halo Properties and Secular Evolution in Barred Galaxies

    NASA Astrophysics Data System (ADS)

    Athanassoula, E.

    The halo plays a crucial role in the evolution of barred galaxies. Its near-resonant material absorbs angular momentum emitted from some of the disc particles and helps the bar become stronger. As a result, a bar (oval) forms in the inner parts of the halo of strongly barred disc galaxies. It is thinner in the inner parts (but still considerably fatter than the disc bar) and tends to spherical at larger radii. Its length increases with time, while always staying shorter than the disc bar. It is roughly aligned with the disc bar, which it trails only slightly, and it turns with roughly the same pattern speed. The bi-symmetric component of the halo density continues well outside the halo bar, where it clearly trails behind the disc bar. The length and strength of the disc and halo bars correlate; the former being always much stronger than the latter. If the halo is composed of weakly interacting massive particles, then the formation of the halo bar, by redistributing the matter in the halo and changing its shape, could influence the expected annihilation signal. This is indeed found to be the case if the halo has a core, but not if it has a steep cusp. The formation and evolution of the bar strongly affect the halo orbits. A fraction of them becomes near-resonant, similar to the disc near-resonant orbits at the same resonance, while another fraction becomes chaotic. Finally, a massive and responsive halo makes it harder for a central mass concentration to destroy the disc bar.

  10. MASS-DEPENDENT BARYON ACOUSTIC OSCILLATION SIGNAL AND HALO BIAS

    SciTech Connect

    Wang Qiao; Zhan Hu

    2013-05-10

    We characterize the baryon acoustic oscillations (BAO) feature in halo two-point statistics using N-body simulations. We find that nonlinear damping of the BAO signal is less severe for halos in the mass range we investigate than for dark matter. The amount of damping depends weakly on the halo mass. The correlation functions show a mass-dependent drop of the halo clustering bias below roughly 90 h {sup -1} Mpc, which coincides with the scale of the BAO trough. The drop of bias is 4% for halos with mass M > 10{sup 14} h {sup -1} M{sub Sun} and reduces to roughly 2% for halos with mass M > 10{sup 13} h {sup -1} M{sub Sun }. In contrast, halo biases in simulations without BAO change more smoothly around 90 h {sup -1} Mpc. In Fourier space, the bias of M > 10{sup 14} h {sup -1} M{sub Sun} halos decreases smoothly by 11% from wavenumber k = 0.012 h Mpc{sup -1} to 0.2 h Mpc{sup -1}, whereas that of M > 10{sup 13} h {sup -1} M{sub Sun} halos decreases by less than 4% over the same range. By comparing the halo biases in pairs of otherwise identical simulations, one with and the other without BAO, we also observe a modulation of the halo bias. These results suggest that precise calibrations of the mass-dependent BAO signal and scale-dependent bias on large scales would be needed for interpreting precise measurements of the two-point statistics of clusters or massive galaxies in the future.

  11. Halos of unified dark matter scalar field

    SciTech Connect

    Bertacca, Daniele; Bartolo, Nicola; Matarrese, Sabino E-mail: nicola.bartolo@pd.infn.it

    2008-05-15

    We investigate the static and spherically symmetric solutions of Einstein's equations for a scalar field with a non-canonical kinetic term, assumed to provide both the dark matter and dark energy components of the Universe. In particular, we give a prescription to obtain solutions (dark halos) whose rotation curve v{sub c}(r) is in good agreement with observational data. We show that there exist suitable scalar field Lagrangians that allow us to describe the cosmological background evolution and the static solutions with a single dark fluid.

  12. Invariant mass spectroscopy of halo nuclei

    SciTech Connect

    Nakamura, Takashi

    2008-11-11

    We have applied the invariant mass spectroscopy to explore the low-lying exited states of halo nuclei at intermediate energies around 70 MeV/nucleon at RIKEN. As examples, we show here the results of Coulomb breakup study for {sup 11}Li using the Pb target, as well as breakup reactions of {sup 14}Be with p and C targets. The former study revealed a strong Coulomb breakup cross section reflecting the large enhancement of E1 strength at low excitation energies (soft E1 excitation). The latter revealed the observation of the first 2{sup +} state in {sup 14}Be.

  13. [A special instrument: the halo fixator].

    PubMed

    Schmolke, Stephan; Gossé, Frank

    2008-03-01

    Installation of an external fixator in combination with a body cast for temporary or definitive immobilization and retention of unstable fractures of the craniocervical junction and upper part of the cervical spine. Further established applications include presurgical extension treatment of paralytic scoliosis and temporary retention within complex spine deformity operations after ventral release or mobilized osteotomies. Closed reposition and temporary retention of unstable injuries of the cervical spine up to operation. Extension treatment for careful reposition of fresh or dated malpositions of the cervical spine. Conservative treatment of injuries of the craniocervical junction and the upper part of the cervical spine. Presurgical extension of paralytic scoliosis. Temporary extension after ventral release. Cranial fractures and intracranial injuries. Soft-tissue infections of the skull. Children < 3 years. Adiposity, chest injuries and paraplegia as relative contraindications using the halo body cast. Halo traction is applied in two stages; first, the head ring is attached to the skull, then, the body cast and suspension assembly are added. Local anesthesia, depending on circumstances. Sizing of the components; the optimal size of the ring is about 1.5" larger than the circumference of the patient's head. Patient in sitting or supine position. The halo ring is held in proper position by stabilizer plates; the lower margin of the ring should be just above the ears and about 0.4" above the eyebrows. The anterior pins are placed in shallow groove on the forehead between supraorbital ridges and frontal protuberances. Threaded skull pins are screwed with defined torque (4-8"/pounds) in the lamina externa of the cranial calotte without perforating the lamina interna. To avoid side-to-side drifting, the diagonally opposite pins should be tightened simultaneously. Finally, connection of the halo ring with a body cast or putting on an extension device. Secure external

  14. Analytical estimation of ATF beam halo distribution

    NASA Astrophysics Data System (ADS)

    Wang, Dou; Philip, Bambade; Kaoru, Yokoya; Gao, Jie

    2014-12-01

    In order to study the backgrounds in the ATF2 beam line and the interaction point (IP), this paper has developed an analytical method to give an estimation of the ATF beam halo distribution based on K. Hirata and K. Yokoya's theory. The equilibrium particle distribution of the beam tail in the ATF damping ring is presented, with each electron affected by several stochastic processes such as beam-gas scattering, beam-gas bremsstrahlung and intra-beam scattering, in addition to the synchrotron radiation damping effects. This is a general method which can also be applied to other electron rings.

  15. Project ECHO: Electronic Communications from Halo Orbit

    NASA Astrophysics Data System (ADS)

    Borrelli, Jason; Cooley, Bryan; Debole, Marcy; Hrivnak, Lance; Nielsen, Kenneth; Sangmeister, Gary; Wolfe, Matthew

    The design of a communications relay to provide constant access between the Earth and the far side of the Moon is presented. Placement of the relay in a halo orbit about the L2 Earth-Moon Lagrange point allows the satellite to maintain constant simultaneous communication between Earth and scientific payloads on the far side of the Moon. The requirements of NASA's Discovery-class missions adopted and modified for this design are: total project cost should not exceed $150 million excluding launch costs, launch must be provided by Delta-class vehicle, and the satellite should maintain an operational lifetime of 10 to 15 years. The spacecraft will follow a transfer trajectory to the L2 point, after launch by a Delta II 7925 vehicle in 1999. Low-level thrust is used for injection into a stationkeeping-free halo orbit once the spacecraft reaches the L2 point. The shape of this halo orbit is highly elliptical with the maximum excursion from the L2 point being 35000 km. A spun section and despun section connected through a bearing and power transfer assembly (BAPTA) compose the structure of the spacecraft. Communications equipment is placed on the despun section to provide for a stationary dual parabolic offset-feed array antenna system. The dual system is necessary to provide communications coverage during portions of maximum excursion on the halo orbit. Transmissions to the NASA Deep Space Network 34 m antenna include six channels (color video, two voice, scientific data from lunar payloads, satellite housekeeping and telemetry and uplinked commands) using the S- and X-bands. Four radioisotope thermoelectric generators (RTG's) provide a total of 1360 W to power onboard systems and any two of the four Hughes 13 cm ion thrusters at once. Output of the ion thrusters is approximately 17.8 mN each with xenon as the propellant. Presence of torques generated by solar pressure on the antenna dish require the addition of a 'skirt' extending from the spun section of the satellite

  16. Cosmic stellar relics in the Galactic halo

    NASA Astrophysics Data System (ADS)

    Salvadori, Stefania; Schneider, Raffaella; Ferrara, Andrea

    2007-10-01

    We study the stellar population history and chemical evolution of the Milky Way (MW) in a hierarchical Λ cold dark matter model for structure formation. Using a Monte Carlo method based on the semi-analytical extended Press & Schechter formalism, we develop a new code GALAXY MERGER TREE AND EVOLUTION (GAMETE) to reconstruct the merger tree of the Galaxy and follow the evolution of gas and stars along the hierarchical tree. Our approach allows us to compare the observational properties of the MW with model results, exploring different properties of primordial stars, such as their initial mass function and the critical metallicity for low-mass star formation, Zcr. In particular, by matching our predictions to the metallicity distribution function (MDF) of metal-poor stars in the Galactic halo we find that: (i) a strong supernova (SN) feedback is required to reproduce the observed properties of the MW; (ii) stars with [Fe/H] < -2.5 form in haloes accreting Galactic medium (GM) enriched by earlier SN explosions; (iii) the fiducial model (Zcr = 10-4Zsolar, mPopIII = 200 Msolar) provides an overall good fit to the MDF, but cannot account for the two hyper-metal-poor (HMP) stars with [Fe/H] < -5 the latter can be accommodated if Zcr <= 10-6 Zsolar but such model overpopulates the `metallicity desert', that is, the range -5.3 < [Fe/H] < -4 in which no stars have been detected; (iv) the current non-detection of metal-free stars robustly constrains either Zcr > 0 or the masses of the first stars mPopIII > 0.9 Msolar (v) the statistical impact of truly second-generation stars, that is, stars forming out of gas polluted only by metal-free stars, is negligible in current samples; and (vi) independent of Zcr, 60 per cent of metals in the GM are ejected through winds by haloes with masses M < 6 × 109 Msolar, thus showing that low-mass haloes are the dominant population contributing to cosmic metal enrichment. We discuss the limitations of our study and comparison with previous

  17. Project ECHO: Electronic Communications from Halo Orbit

    NASA Technical Reports Server (NTRS)

    Borrelli, Jason; Cooley, Bryan; Debole, Marcy; Hrivnak, Lance; Nielsen, Kenneth; Sangmeister, Gary; Wolfe, Matthew

    1994-01-01

    The design of a communications relay to provide constant access between the Earth and the far side of the Moon is presented. Placement of the relay in a halo orbit about the L2 Earth-Moon Lagrange point allows the satellite to maintain constant simultaneous communication between Earth and scientific payloads on the far side of the Moon. The requirements of NASA's Discovery-class missions adopted and modified for this design are: total project cost should not exceed $150 million excluding launch costs, launch must be provided by Delta-class vehicle, and the satellite should maintain an operational lifetime of 10 to 15 years. The spacecraft will follow a transfer trajectory to the L2 point, after launch by a Delta II 7925 vehicle in 1999. Low-level thrust is used for injection into a stationkeeping-free halo orbit once the spacecraft reaches the L2 point. The shape of this halo orbit is highly elliptical with the maximum excursion from the L2 point being 35000 km. A spun section and despun section connected through a bearing and power transfer assembly (BAPTA) compose the structure of the spacecraft. Communications equipment is placed on the despun section to provide for a stationary dual parabolic offset-feed array antenna system. The dual system is necessary to provide communications coverage during portions of maximum excursion on the halo orbit. Transmissions to the NASA Deep Space Network 34 m antenna include six channels (color video, two voice, scientific data from lunar payloads, satellite housekeeping and telemetry and uplinked commands) using the S- and X-bands. Four radioisotope thermoelectric generators (RTG's) provide a total of 1360 W to power onboard systems and any two of the four Hughes 13 cm ion thrusters at once. Output of the ion thrusters is approximately 17.8 mN each with xenon as the propellant. Presence of torques generated by solar pressure on the antenna dish require the addition of a 'skirt' extending from the spun section of the satellite

  18. Sign Lowering and Phonetic Reduction in American Sign Language

    PubMed Central

    Tyrone, Martha E.; Mauk, Claude E.

    2010-01-01

    This study examines sign lowering as a form of phonetic reduction in American Sign Language. Phonetic reduction occurs in the course of normal language production, when instead of producing a carefully articulated form of a word, the language user produces a less clearly articulated form. When signs are produced in context by native signers, they often differ from the citation forms of signs. In some cases, phonetic reduction is manifested as a sign being produced at a lower location than in the citation form. Sign lowering has been documented previously, but this is the first study to examine it in phonetic detail. The data presented here are tokens of the sign WONDER, as produced by six native signers, in two phonetic contexts and at three signing rates, which were captured by optoelectronic motion capture. The results indicate that sign lowering occurred for all signers, according to the factors we manipulated. Sign production was affected by several phonetic factors that also influence speech production, namely, production rate, phonetic context, and position within an utterance. In addition, we have discovered interesting variations in sign production, which could underlie distinctions in signing style, analogous to accent or voice quality in speech. PMID:20607146

  19. Sign Language Comprehension: The Case of Spanish Sign Language

    ERIC Educational Resources Information Center

    Rodriguez Ortiz, I. R.

    2008-01-01

    This study aims to answer the question, how much of Spanish Sign Language interpreting deaf individuals really understand. Study sampling included 36 deaf people (deafness ranging from severe to profound; variety depending on the age at which they learned sign language) and 36 hearing people who had good knowledge of sign language (most were…

  20. Sign Language Comprehension: The Case of Spanish Sign Language

    ERIC Educational Resources Information Center

    Rodriguez Ortiz, I. R.

    2008-01-01

    This study aims to answer the question, how much of Spanish Sign Language interpreting deaf individuals really understand. Study sampling included 36 deaf people (deafness ranging from severe to profound; variety depending on the age at which they learned sign language) and 36 hearing people who had good knowledge of sign language (most were…

  1. Expedition 39 Door Signing

    NASA Image and Video Library

    2014-03-25

    Expedition 39 Soyuz Commander Alexander Skvortsov of the Russian Federal Space Agency, Roscosmos, performs the traditional door signing at the Cosmonaut hotel prior to departing the hotel for launch in a Soyuz rocket with fellow crew mates, Flight Engineer Steve Swanson of NASA and Flight Engineer Oleg Artemyev of Roscosmos, Tuesday, March 25, 2014, in Baikonur, Kazakhstan. Skvortsov, Swanson, and Artemyev will launch in their Soyuz TMA-12M spacecraft to the International Space Station to begin a six-month mission. Photo Credit (NASA/Joel Kowsky)

  2. Expedition 42 Door Signing

    NASA Image and Video Library

    2014-11-23

    Expedition 42 Soyuz Commander Anton Shkaplerov of the Russian Federal Space Agency (Roscosmos) performs the traditional door signing at the Cosmonaut Hotel prior to departing the hotel for launch in a Soyuz rocket with fellow crewmates, Flight Engineers Samantha Cristoforetti of the European Space Agency (ESA) and Terry Virts of NASA, Sunday, Nov. 23, 2014 in Baikonur, Kazakhstan. Launch of the Soyuz rocket is scheduled for the early hours of Nov. 24 Kazakhstan time and will carry Shkaplerov, Cristoforetti, and Virts into orbit to begin their five and a half month mission on the International Space Station. Photo Credit (NASA/Aubrey Gemignani)

  3. Expedition 42 Door Signing

    NASA Image and Video Library

    2014-11-23

    Expedition 42 Flight Engineer Terry Virts of NASA performs the traditional door signing at the Cosmonaut Hotel prior to departing the hotel for launch in a Soyuz rocket with fellow crewmates, Soyuz Commander Anton Shkaplerov of the Russian Federal Space Agency (Roscosmos) and Flight Engineer Samantha Cristoforetti of the European Space Agency (ESA), Sunday, Nov. 23, 2014 in Baikonur, Kazakhstan. Launch of the Soyuz rocket is scheduled for the early hours of Nov. 24 Kazakhstan time and will carry Virts, Shkaplerov, and Cristoforetti into orbit to begin their five and a half month mission on the International Space Station. Photo Credit: (NASA/Aubrey Gemignani)

  4. Expedition 39 Door Signing

    NASA Image and Video Library

    2014-03-25

    Expedition 39 Flight Engineer Oleg Artemyev of the Russian Federal Space Agency, Roscosmos, performs the traditional door signing at the Cosmonaut hotel prior to departing the hotel for launch in a Soyuz rocket with fellow crew mates, Soyuz Commander Alexander Skvortsov of Roscosmos, and Flight Engineer Steve Swanson of NASA, Tuesday, March 25, 2014, in Baikonur, Kazakhstan. Artemyev, Skvortsov, and Swanson will launch in their Soyuz TMA-12M spacecraft to the International Space Station to begin a six-month mission. Photo Credit (NASA/Joel Kowsky)

  5. Expedition 39 Door Signing

    NASA Image and Video Library

    2014-03-25

    Expedition 39 Flight Engineer Steve Swanson of NASA, performs the traditional door signing at the Cosmonaut hotel prior to departing the hotel for launch in a Soyuz rocket with fellow crew mates, Soyuz Commander Alexander Skvortsov of the Russian Federal Space Agency, Roscosmos, and Flight Engineer Oleg Artemyev of Roscosmos, Tuesday, March 25, 2014, in Baikonur, Kazakhstan. Swanson, Skvortsov and, and Artemyev will launch in their Soyuz TMA-12M spacecraft to the International Space Station to begin a six-month mission. Photo Credit (NASA/Joel Kowsky)

  6. Expedition 42 Door Signing

    NASA Image and Video Library

    2014-11-23

    Expedition 42 Flight Engineer Samantha Cristoforetti of the European Space Agency (ESA), performs the traditional door signing at the Cosmonaut Hotel prior to departing the hotel for launch in a Soyuz rocket with fellow crewmates, Soyuz Commander Anton Shkaplerov of the Russian Federal Space Agency (Roscosmos) and Flight Engineer Terry Virts of NASA, Sunday, Nov. 23, 2014 in Baikonur, Kazakhstan. Launch of the Soyuz rocket is scheduled for the early hours of Nov. 24 Kazakhstan time and will carry Cristoforetti, Virts, and Shkaplerov into orbit to begin their five and a half month mission on the International Space Station. Photo Credit (NASA/Aubrey Gemignani)

  7. Seeing the signs.

    PubMed

    Blewitt, Jane

    2016-04-01

    Invasive meningococcal disease, causing meningitis and/or septicaemia, can kill within hours and leave a significant number of survivors with lifelong disability. Even though there are now three meningococcal vaccines in the U.K. routine immunisation schedule, not all cases will be prevented. There are also other bacterial, viral and fungal causes of meningitis that are not prevented by vaccines, it is too early to assess the impact of recent changes to the schedule and it is vital that everyone is aware of the signs and symptoms, and remains vigilant.

  8. Sign of coma.

    PubMed

    Skjaerlund, J M

    1988-06-15

    The oblique focusing defect of spherical lenses, known as coma, is described by Seidel as the second of five correction terms (third order) to the Gauss theory. The concept is clear for a refracting surface that is free of spherical aberration; however, the impossibility of eliminating spherical aberration from a single lens with spherical surfaces can confuse the understanding of the second aberration, coma. A way of understanding the comatic effect even in the presence of spherical aberration is described. Confusion over the sign of coma, as indicated by mistakes in optics textbooks, is addressed. This paper suggests corrections to some interpretations of coma found in the literature.

  9. Vasectomy reversal.

    PubMed

    Belker, A M

    1987-02-01

    A vasovasostomy may be performed on an outpatient basis with local anesthesia, but also may be performed on an outpatient basis with epidural or general anesthesia. Local anesthesia is preferred by most of my patients, the majority of whom choose this technique. With proper preoperative and intraoperative sedation, patients sleep lightly through most of the procedure. Because of the length of time often required for bilateral microsurgical vasoepididymostomy, epidural or general anesthesia and overnight hospitalization are usually necessary. Factors influencing the preoperative choice for vasovasostomy or vasoepididymostomy in patients undergoing vasectomy reversal are considered. The preoperative planned choice of vasovasostomy or vasoepididymostomy for patients having vasectomy reversal described herein does not have the support of all urologists who regularly perform these procedures. My present approach has evolved as the data reported in Tables 1 and 2 have become available, but it may change as new information is evaluated. However, it offers a logical method for planning choices of anesthesia and inpatient or outpatient status for patients undergoing vasectomy reversal procedures.

  10. Signs of a Heart Attack

    MedlinePlus

    ... attack Heart Health and Stroke Signs of a heart attack Related information Make the Call. Don't Miss ... to top More information on Signs of a heart attack Read more from womenshealth.gov Make the Call, ...

  11. Warning Signs of Lung Disease

    MedlinePlus

    ... Warning Signs of Lung Disease Warning Signs of Lung Disease A nagging cough or slight wheeze may ... prepare for you next office visit. Questions about Lung Health? Call our Lung HelpLine. Get free counseling ...

  12. The Dependence of the Occupation of Galaxies on the Halo Formation Time

    NASA Astrophysics Data System (ADS)

    Zhu, Guangtun; Zheng, Zheng; Lin, W. P.; Jing, Y. P.; Kang, Xi; Gao, Liang

    2006-03-01

    We study the dependence of the galaxy contents within halos on the halo formation time using two galaxy formation models, one being a semianalytic model utilizing the halo assembly history from a high-resolution N-body simulation and the other being a smoothed particle hydrodynamics simulation including radiative cooling, star formation, and energy feedback from galactic winds. We confirm the finding by Gao et al. that at fixed mass, the clustering of halos depends on the halo formation time, especially for low-mass halos. This age dependence of halo clustering makes it desirable to study the correlation between the occupation of galaxies within halos and the halo age. We find that, in halos of fixed mass, the number of satellite galaxies has a strong dependence on halo age, with fewer satellites in older halos. The youngest one-third of the halos can have an order of magnitude more satellites than the oldest one-third. For central galaxies, in halos that form earlier, they tend to have more stars and thus appear to be more luminous, and the dependence of their luminosity on halo age is not as strong as that of stellar mass. The results can be understood through the star formation history in halos and the merging of satellites onto central galaxies. The age dependence of the galaxy contents within halos would constitute an important ingredient in a more accurate halo-based model of galaxy clustering.

  13. Simultaneous Visualization of Parental and Progeny Viruses by a Capsid-Specific HaloTag Labeling Strategy.

    PubMed

    Liu, An-An; Zhang, Zhenfeng; Sun, En-Ze; Zheng, Zhenhua; Zhang, Zhi-Ling; Hu, Qinxue; Wang, Hanzhong; Pang, Dai-Wen

    2016-01-26

    Real-time, long-term, single-particle tracking (SPT) provides us an opportunity to explore the fate of individual viruses toward understanding the mechanisms underlying virus infection, which in turn could lead to the development of therapeutics against viral diseases. However, the research focusing on the virus assembly and egress by SPT remains a challenge because established labeling strategies could neither specifically label progeny viruses nor make them distinguishable from the parental viruses. Herein, we have established a temporally controllable capsid-specific HaloTag labeling strategy based on reverse genetic technology. VP26, the smallest pseudorabies virus (PrV) capsid protein, was fused with HaloTag protein and labeled with the HaloTag ligand during virus replication. The labeled replication-competent recombinant PrV harvested from medium can be applied directly in SPT experiments without further modification. Thus, virus infectivity, which is critical for the visualization and analysis of viral motion, is retained to the largest extent. Moreover, progeny viruses can be distinguished from parental viruses using diverse HaloTag ligands. Consequently, the entire course of virus infection and replication can be visualized continuously, including virus attachment and capsid entry, transportation of capsids to the nucleus along microtubules, docking of capsids on the nucleus, endonuclear assembly of progeny capsids, and the egress of progeny viruses. In combination with SPT, the established strategy represents a versatile means to reveal the mechanisms and dynamic global picture of the life cycle of a virus.

  14. The Edges Of Dark Matter Halos: Theory And Observations

    NASA Astrophysics Data System (ADS)

    More, Surhud

    2017-06-01

    I discuss recent theoretical advances which have led us to suggest a physical definition for the boundary of dark matter halos. We propose using the "splashback radius" which corresponds to the apocenter of recently infalling material as a physical boundary for dark matter halos. We also present how the splashback radius can be detected in observations.

  15. Beam halo definitions based upon moments of the particle distribution

    NASA Astrophysics Data System (ADS)

    Allen, C. K.; Wangler, T. P.

    2002-12-01

    Two different parameters for the quantitative description of beam halo are discussed. Both are based on moments of the particle distribution and represent a convenient and model-independent method for quantifying the magnitude of beam halo observed in either spatial or phase-space projections. One parameter is a measure of spatial profile of the beam and has been defined by Wangler and Crandall previously. The current authors defined a new parameter using kinematic invariants to quantify halo formation in 2D phase space. Here we expand the development and present detailed numerical results. Although the spatial-profile parameter and the phase-space halo parameter both reduce to the same value when the distribution has the elliptical symmetry, in general these parameters are not equal. Halo in the 1D spatial profiles is relatively easily measured, but is variable as the beam distribution evolves and can hide as it rotates in phase space. The 2D phase-space halo is more difficult to measure, but it varies more smoothly as the halo evolves. It provides a more reliable characterization of the halo as an intrinsic property of the beam.

  16. Remarks on the spherical scalar field halo in galaxies

    SciTech Connect

    Nandi, Kamal K.; Valitov, Ildar; Migranov, Nail G.

    2009-08-15

    Matos, Guzman, and Nunez proposed a model for the galactic halo within the framework of scalar field theory. We argue that an analysis involving the full metric can reveal the true physical nature of the halo only when a certain condition is maintained. We fix that condition and also calculate its impact on observable parameters of the model.

  17. Halo-Independent Comparison of Direct Dark Matter Detection Data

    DOE PAGES

    Del Nobile, Eugenio

    2014-01-01

    We review the halo-independent formalism that allows comparing data from different direct dark matter detection experiments without making assumptions on the properties of the dark matter halo. We apply this method to spin-independent WIMP-nuclei interactions, for both isospin-conserving and isospin-violating couplings, and to WIMPs interacting through an anomalous magnetic moment.

  18. Lyman-Werner UV escape fractions from primordial haloes

    NASA Astrophysics Data System (ADS)

    Schauer, Anna T. P.; Whalen, Daniel J.; Glover, Simon C. O.; Klessen, Ralf S.

    2015-12-01

    Population III (Pop III) stars can regulate star formation in the primordial Universe in several ways. They can ionize nearby haloes, and even if their ionizing photons are trapped by their own haloes, their Lyman-Werner (LW) photons can still escape and destroy H2 in other haloes, preventing them from cooling and forming stars. LW escape fractions are thus a key parameter in cosmological simulations of early reionization and star formation but have not yet been parametrized for realistic haloes by halo or stellar mass. To do so, we perform radiation hydrodynamical simulations of LW UV escape from 9-120 M⊙ Pop III stars in 105-107 M⊙ haloes with ZEUS-MP. We find that photons in the LW lines (i.e. those responsible for destroying H2 in nearby systems) have escape fractions ranging from 0 to 85 per cent. No LW photons escape the most massive halo in our sample, even from the most massive star. Escape fractions for photons elsewhere in the 11.18-13.6 eV energy range, which can be redshifted into the LW lines at cosmological distances, are generally much higher, being above 60 per cent for all but the least massive stars in the most massive haloes. We find that shielding of H2 by neutral hydrogen, which has been neglected in most studies to date, produces escape fractions that are up to a factor of 3 smaller than those predicted by H2 self-shielding alone.

  19. The prolate dark matter halo of the Andromeda galaxy

    SciTech Connect

    Hayashi, Kohei; Chiba, Masashi E-mail: chiba@astr.tohoku.ac.jp

    2014-07-01

    We present new limits on the global shape of the dark matter halo in the Andromeda galaxy using and generalizing non-spherical mass models developed by Hayashi and Chiba and compare our results with theoretical predictions of cold dark matter (CDM) models. This is motivated by the fact that CDM models predict non-spherical virialized dark halos, which reflect the process of mass assembly in the galactic scale. Applying our models to the latest kinematic data of globular clusters and dwarf spheroidal galaxies in the Andromeda halo, we find that the most plausible cases for Andromeda yield a prolate shape for its dark halo, irrespective of assumed density profiles. We also find that this prolate dark halo in Andromeda is consistent with theoretical predictions in which the satellites are distributed anisotropically and preferentially located along major axes of their host halos. It is a reflection of the intimate connection between galactic dark matter halos and the cosmic web. Therefore, our result is profound in understanding internal dynamics of halo tracers in Andromeda, such as orbital evolutions of tidal stellar streams, which play important roles in extracting the abundance of CDM subhalos through their dynamical effects on stream structures.

  20. SECULAR DAMPING OF STELLAR BARS IN SPINNING DARK MATTER HALOS

    SciTech Connect

    Long, Stacy; Shlosman, Isaac; Heller, Clayton

    2014-03-01

    We demonstrate using numerical simulations of isolated galaxies that growth of stellar bars in spinning dark matter halos is heavily suppressed in the secular phase of evolution. In a representative set of models, we show that for values of the cosmological spin parameter λ ≳ 0.03, bar growth (in strength and size) becomes increasingly quenched. Furthermore, the slowdown of the bar pattern speed weakens considerably with increasing λ until it ceases completely. The terminal structure of the bars is affected as well, including extent and shape of their boxy/peanut bulges. The essence of this effect lies in the modified angular momentum exchange between the disk and the halo facilitated by the bar. For the first time we have demonstrated that a dark matter halo can emit and not purely absorb angular momentum. Although the halo as a whole is not found to emit, the net transfer of angular momentum from the disk to the halo is significantly reduced or completely eliminated. The paradigm shift implies that the accepted view that disks serve as sources of angular momentum and halos serve as sinks must be revised. Halos with λ ≳ 0.03 are expected to form a substantial fraction, based on the lognormal distribution of λ. The dependence of secular bar evolution on halo spin, therefore, implies profound corollaries for the cosmological evolution of galactic disks.

  1. Investigating Halo and Ceiling Effects in Student Evaluations of Instruction

    ERIC Educational Resources Information Center

    Keeley, Jared W.; English, Taylor; Irons, Jessica; Henslee, Amber M.

    2013-01-01

    Many measurement biases affect student evaluations of instruction (SEIs). However, two have been relatively understudied: halo effects and ceiling/floor effects. This study examined these effects in two ways. To examine the halo effect, using a videotaped lecture, we manipulated specific teacher behaviors to be "good" or "bad"…

  2. Detecting Halo Effects in Performance-Based Examinations

    ERIC Educational Resources Information Center

    Bechger, Timo M.; Maris, Gunter; Hsiao, Ya Ping

    2010-01-01

    The main purpose of this article is to demonstrate how halo effects may be detected and quantified using two independent ratings of the same person. A practical illustration is given to show how halo effects can be avoided. (Contains 2 tables, 7 figures, and 2 notes.)

  3. Investigating Halo and Ceiling Effects in Student Evaluations of Instruction

    ERIC Educational Resources Information Center

    Keeley, Jared W.; English, Taylor; Irons, Jessica; Henslee, Amber M.

    2013-01-01

    Many measurement biases affect student evaluations of instruction (SEIs). However, two have been relatively understudied: halo effects and ceiling/floor effects. This study examined these effects in two ways. To examine the halo effect, using a videotaped lecture, we manipulated specific teacher behaviors to be "good" or "bad"…

  4. Detecting Halo Effects in Performance-Based Examinations

    ERIC Educational Resources Information Center

    Bechger, Timo M.; Maris, Gunter; Hsiao, Ya Ping

    2010-01-01

    The main purpose of this article is to demonstrate how halo effects may be detected and quantified using two independent ratings of the same person. A practical illustration is given to show how halo effects can be avoided. (Contains 2 tables, 7 figures, and 2 notes.)

  5. The segregation of baryons and dark matter during halo assembly

    NASA Astrophysics Data System (ADS)

    Liao, Shihong; Gao, Liang; Frenk, Carlos S.; Guo, Qi; Wang, Jie

    2017-09-01

    The standard galaxy formation theory assumes that baryons and dark matter are initially well mixed before becoming segregated due to radiative cooling. We use non-radiative hydrodynamical simulations to explicitly examine this assumption and find that baryons and dark matter can also be segregated due to different characteristics of gas and dark matter during the buildup of the halo. As a result, baryons in many haloes do not originate from the same Lagrangian region as the dark matter. When using the fraction of corresponding dark matter and gas particles in the initial conditions (the 'paired fraction') as a proxy of the dark matter and gas segregation strength of a halo, on average about 25 per cent of the baryonic and dark matter of the final halo are segregated in the initial conditions. This is at odds with the assumption of the standard galaxy formation model. A consequence of this effect is that the baryons and dark matter of the same halo initially experience different tidal torques and thus their angular momentum vectors are often misaligned. The degree of the misalignment is largely preserved during later halo assembly and can be understood with the tidal torque theory. The result challenges the precision of some semi-analytical approaches that utilize dark matter halo merger trees to infer properties of gas associated with dark matter haloes.

  6. INFINITY construction contract signed

    NASA Image and Video Library

    2010-04-06

    Key state and community leaders celebrated April 6 with the signing of a construction contract for the state-of-the-art INFINITY Science Center planned near John C. Stennis Space Center in south Mississippi. Gulfport Mayor George Schloegel (l to r), chair of non-profit INFINITY Science Center Inc., was joined for the signing ceremony at the Hancock Bank in Gulfport by Virginia Wagner, sister of late Hancock Bank President Leo Seal Jr.; and Roy Anderson III, president and CEO of Roy Anderson Corp. Seal was the first chair of INFINITY Science Center Inc., which has led in development of the project. Roy Anderson Corp. plans to begin construction on the 72,000-square-foot, $28 million science and education center in May. The Mississippi Department of Transportation (MDOT) also is set to begin construction of a $2 million access road to the new center. The April 6 ceremony was attended by numerous officials, including former Stennis Space Center Directors Jerry Hlass and Roy Estess; Mississippi Senate President Pro Tempore Billy Hewes, R-Gulfport; Mississippi Rep. Diane Peranich, D-Pass Christian; and MDOT Southern District Commissioner Wayne Brown.

  7. INFINITY construction contract signed

    NASA Technical Reports Server (NTRS)

    2010-01-01

    Key state and community leaders celebrated April 6 with the signing of a construction contract for the state-of-the-art INFINITY Science Center planned near John C. Stennis Space Center in south Mississippi. Gulfport Mayor George Schloegel (l to r), chair of non-profit INFINITY Science Center Inc., was joined for the signing ceremony at the Hancock Bank in Gulfport by Virginia Wagner, sister of late Hancock Bank President Leo Seal Jr.; and Roy Anderson III, president and CEO of Roy Anderson Corp. Seal was the first chair of INFINITY Science Center Inc., which has led in development of the project. Roy Anderson Corp. plans to begin construction on the 72,000-square-foot, $28 million science and education center in May. The Mississippi Department of Transportation (MDOT) also is set to begin construction of a $2 million access road to the new center. The April 6 ceremony was attended by numerous officials, including former Stennis Space Center Directors Jerry Hlass and Roy Estess; Mississippi Senate President Pro Tempore Billy Hewes, R-Gulfport; Mississippi Rep. Diane Peranich, D-Pass Christian; and MDOT Southern District Commissioner Wayne Brown.

  8. INFINITY construction contract signed

    NASA Technical Reports Server (NTRS)

    2010-01-01

    Key state and community leaders celebrated April 6 with the signing of a construction contract for the state-of-the-art INFINITY Science Center planned near John C. Stennis Space Center in south Mississippi. Gulfport Mayor George Schloegel (l to r), chair of non-profit INFINITY Science Center Inc., was joined for the signing ceremony at the Hancock Bank in Gulfport by Virginia Wagner, sister of late Hancock Bank President Leo Seal Jr.; and Roy Anderson III, president and CEO of Roy Anderson Corp. Seal was the first chair of INFINITY Science Center Inc., which has led in development of the project. Roy Anderson Corp. plans to begin construction on the 72,000-square-foot, $28 million science and education center in May. The Mississippi Department of Transportation (MDOT) also is set to begin construction of a $2 million access road to the new center. The April 6 ceremony was attended by numerous officials, including former Stennis Space Center Directors Jerry Hlass and Roy Estess; Mississippi Senate President Pro Tempore Billy Hewes, R-Gulfport; Mississippi Rep. Diane Peranich, D-Pass Christian; and MDOT Southern District Commissioner Wayne Brown.

  9. Frost halos from supercooled water droplets

    PubMed Central

    Jung, Stefan; Tiwari, Manish K.; Poulikakos, Dimos

    2012-01-01

    Water freezing on solid surfaces is ubiquitous in nature. Even though icing/frosting impairs the performance and safety in many processes, its mechanism remains inadequately understood. Changing atmospheric conditions, surface properties, the complexity of icing physics, and the unorthodox behavior of water are the primary factors that make icing and frost formation intriguing and difficult to predict. In addition to its unquestioned scientific and practical importance, unraveling the frosting mechanism under different conditions is a prerequisite to develop “icephobic” surfaces, which may avoid ice formation and contamination. In this work we demonstrate that evaporation from a freezing supercooled sessile droplet, which starts explosively due to the sudden latent heat released upon recalescent freezing, generates a condensation halo around the droplet, which crystallizes and drastically affects the surface behavior. The process involves simultaneous multiple phase transitions and may also spread icing by initiating sequential freezing of neighboring droplets in the form of a domino effect and frost propagation. Experiments under controlled humidity conditions using substrates differing up to three orders of magnitude in thermal conductivity establish that a delicate balance between heat diffusion and vapor transport determines the final expanse of the frozen condensate halo, which, in turn, controls frost formation and propagation. PMID:23012410

  10. Halogen Occultation Experiment (HALOE) optical filter characterization

    NASA Technical Reports Server (NTRS)

    Harvey, Gale A.

    1989-01-01

    The Halogen Occultation Experiment (HALOE) is a solar occultation experiment that will fly on the Upper Atmosphere Research Satellite to measure mixing ratio profiles of O3, H2O, NO2, NO, CH4, HCl, and HF. The inversion of the HALOE data will be critically dependent on a detailed knowledge of eight optical filters. A filter characterization program was undertaken to measure in-band transmissions, out-of-band transmissions, in-band transmission shifts with temperature, reflectivities, and age stability. Fourier Transform Infrared Spectrometers were used to perform measurements over the spectral interval 400/cm to 6300/cm (25 micrometers to 1.6 micrometers). Very high precision (0.1 percent T) in-band measurements and very high resolution (0.0001 percent T) out-of-band measurements have been made. The measurements revealed several conventional leaks at 0.01 percent transmission and greatly enhanced (1,000) leaks to the 2-element filters when placed in a Fabry-Perot cavity. Filter throughput changes by 5 percent for a 25 C change in filter temperature.

  11. Halo clustering with nonlocal non-Gaussianity

    SciTech Connect

    Schmidt, Fabian; Kamionkowski, Marc

    2010-11-15

    We show how the peak-background split (PBS) can be generalized to predict the effect of nonlocal primordial non-Gaussianity on the clustering of halos. Our approach is applicable to arbitrary primordial bispectra. We show that the scale dependence of halo clustering predicted in the peak-background split agrees with that of the local-biasing model on large scales. On smaller scales, k > or approx. 0.01h Mpc{sup -1}, the predictions diverge, a consequence of the assumption of separation of scales in the peak-background split. Even on large scales, PBS and local biasing do not generally agree on the amplitude of the effect outside of the high-peak limit. The scale dependence of the biasing - the effect that provides strong constraints to the local-model bispectrum - is far weaker for the equilateral and self-ordering-scalar-field models of non-Gaussianity. The bias scale dependence for the orthogonal and folded models is weaker than in the local model ({approx}k{sup -1}), but likely still strong enough to be constraining. We show that departures from scale-invariance of the primordial power spectrum may lead to order-unity corrections, relative to predictions made assuming scale-invariance--to the non-Gaussian bias in some of these nonlocal models for non-Gaussianity. An Appendix shows that a nonlocal model can produce the local-model bispectrum, a mathematical curiosity we uncovered in the course of this investigation.

  12. HALOE Algorithm Improvements for Upper Tropospheric Sounding

    NASA Technical Reports Server (NTRS)

    McHugh, Martin J.; Gordley, Larry L.; Russell, James M., III; Hervig, Mark E.

    1999-01-01

    This report details the ongoing efforts by GATS, Inc., in conjunction with Hampton University and University of Wyoming, in NASA's Mission to Planet Earth UARS Science Investigator Program entitled "HALOE Algorithm Improvements for Upper Tropospheric Soundings." The goal of this effort is to develop and implement major inversion and processing improvements that will extend HALOE measurements further into the troposphere. In particular, O3, H2O, and CH4 retrievals may be extended into the middle troposphere, and NO, HCl and possibly HF into the upper troposphere. Key areas of research being carried out to accomplish this include: pointing/tracking analysis; cloud identification and modeling; simultaneous multichannel retrieval capability; forward model improvements; high vertical-resolution gas filter channel retrievals; a refined temperature retrieval; robust error analyses; long-term trend reliability studies; and data validation. The current (first-year) effort concentrates on the pointer/tracker correction algorithms, cloud filtering and validation, and multi-channel retrieval development. However, these areas are all highly coupled, so progress in one area benefits from and sometimes depends on work in others.

  13. HALOE Algorithm Improvements for Upper Tropospheric Sounding

    NASA Technical Reports Server (NTRS)

    Thompson, Robert E.

    2001-01-01

    This report details the ongoing efforts by GATS, Inc., in conjunction with Hampton University and University of Wyoming, in NASA's Mission to Planet Earth UARS Science Investigator Program entitled "HALOE Algorithm Improvements for Upper Tropospheric Sounding." The goal of this effort is to develop and implement major inversion and processing improvements that will extend HALOE measurements further into the troposphere. In particular, O3, H2O, and CH4 retrievals may be extended into the middle troposphere, and NO, HCl and possibly HF into the upper troposphere. Key areas of research being carried out to accomplish this include: pointing/tracking analysis; cloud identification and modeling; simultaneous multichannel retrieval capability; forward model improvements; high vertical-resolution gas filter channel retrievals; a refined temperature retrieval; robust error analyses; long-term trend reliability studies; and data validation. The current (first year) effort concentrates on the pointer/tracker correction algorithms, cloud filtering and validation, and multichannel retrieval development. However, these areas are all highly coupled, so progress in one area benefits from and sometimes depends on work in others.

  14. HALOE Algorithm Improvements for Upper Tropospheric Soundings

    NASA Technical Reports Server (NTRS)

    Thompson, Robert E.; Douglass, Anne (Technical Monitor)

    2000-01-01

    This report details the ongoing efforts by GATS, Inc., in conjunction with Hampton University and University of Wyoming, in NASA's Mission to Planet Earth UARS Science Investigator Program entitled "HALOE Algorithm Improvements for Upper Tropospheric Sounding." The goal of this effort is to develop and implement major inversion and processing improvements that will extend HALOE measurements further into the troposphere. In particular, O3, H2O, and CH4 retrievals may be extended into the middle troposphere, and NO, HCl and possibly HF into the upper troposphere. Key areas of research being carried out to accomplish this include: pointing/tracking analysis; cloud identification and modeling; simultaneous multichannel retrieval capability; forward model improvements; high vertical-resolution gas filter channel retrievals; a refined temperature retrieval; robust error analyses; long-term trend reliability studies; and data validation. The current (first year) effort concentrates on the pointer/tracker correction algorithms, cloud filtering and validation, and multichannel retrieval development. However, these areas are all highly coupled, so progress in one area benefits from and sometimes depends on work in others.

  15. HALOE Algorithm Improvements for Upper Tropospheric Sounding

    NASA Technical Reports Server (NTRS)

    Thompson, Robert Earl; McHugh, Martin J.; Gordley, Larry L.; Hervig, Mark E.; Russell, James M., III; Douglass, Anne (Technical Monitor)

    2001-01-01

    This report details the ongoing efforts by GATS, Inc., in conjunction with Hampton University and University of Wyoming, in NASA's Mission to Planet Earth Upper Atmospheric Research Satellite (UARS) Science Investigator Program entitled 'HALOE Algorithm Improvements for Upper Tropospheric Sounding.' The goal of this effort is to develop and implement major inversion and processing improvements that will extend Halogen Occultation Experiment (HALOE) measurements further into the troposphere. In particular, O3, H2O, and CH4 retrievals may be extended into the middle troposphere, and NO, HCl and possibly HF into the upper troposphere. Key areas of research being carried out to accomplish this include: pointing/tracking analysis; cloud identification and modeling; simultaneous multichannel retrieval capability; forward model improvements; high vertical-resolution gas filter channel retrievals; a refined temperature retrieval; robust error analyses; long-term trend reliability studies; and data validation. The current (first year) effort concentrates on the pointer/tracker correction algorithms, cloud filtering and validation, and multichannel retrieval development. However, these areas are all highly coupled, so progress in one area benefits from and sometimes depends on work in others.

  16. MACHO (MAssive Compact Halo Objects) Data

    DOE Data Explorer

    The primary aim of the MACHO Project is to test the hypothesis that a significant fraction of the dark matter in the halo of the Milky Way is made up of objects like brown dwarfs or planets: these objects have come to be known as MACHOs, for MAssive Compact Halo Objects. The signature of these objects is the occasional amplification of the light from extragalactic stars by the gravitational lens effect. The amplification can be large, but events are extremely rare: it is necessary to monitor photometrically several million stars for a period of years in order to obtain a useful detection rate. For this purpose MACHO has a two channel system that employs eight CCDs, mounted on the 50 inch telescope at Mt. Stromlo. The high data rate (several GBytes per night) is accommodated by custom electronics and on-line data reduction. The Project has taken more than 27,000 images with this system since June 1992. Analysis of a subset of these data has yielded databases containing light curves in two colors for 8 million stars in the LMC and 10 million in the bulge of the Milky Way. A search for microlensing has turned up four candidates toward the Large Magellanic Cloud and 45 toward the Galactic Bulge. The web page for data provides links to MACHO Project data portals and various specialized interfaces for viewing or searching the data. (Specialized Interface)

  17. Inhomogeneous chemical enrichment in the Galactic Halo

    NASA Astrophysics Data System (ADS)

    Kobayashi, Chiaki

    2016-08-01

    In a galaxy, chemical enrichment takes place in an inhomogeneous fashion, and the Galactic Halo is one of the places where the inhomogeneous effects are imprinted and can be constrained from observations. I show this using my chemodynamical simulations of Milky Way type galaxies. The scatter in the elemental abundances originate from radial migration, merging/accretion of satellite galaxies, local variation of star formation and chemical enrichment, and intrinsic variation of nucleosynthesis yields. In the simulated galaxies, there is no strong age-metallicity relation. This means that the most metal-poor stars are not always the oldest stars, and can be formed in chemically unevolved clouds at later times. The long-lifetime sources of chemical enrichment such as asymptotic giant branch stars or neutron star mergers can contribute at low metallicities. The intrinsic variation of yields are important in the early Universe or metal-poor systems such as in the Galactic halo. The carbon enhancement of extremely metal-poor (EMP) stars can be best explained by faint supernovae, the low [α/Fe] ratios in some EMP stars naturally arise from low-mass (~ 13 - 15M ⊙) supernovae, and finally, the [α/Fe] knee in dwarf spheroidal galaxies can be produced by subclasses of Type Ia supernovae such as SN 2002cx-like objects and sub-Chandrasekhar mass explosions.

  18. Detecting Halo Substructure in the Gaia Era

    NASA Astrophysics Data System (ADS)

    Mateu, C.; Aguilar, L.; Bruzual, G.; Brown, A.; Valenzuela, O.; Carigi, L.; Velázquez, H.; Hernández, F.

    2014-06-01

    The observational data expected to come from the Gaia astrometric mission represent an unrivaled opportunity to search for tidal streams using all-sky full phase-space information for nearly a billion stars in our Galaxy. In this contribution we will describe the Modified Great Circle Cell Count (mGC3) method devised for the detection of stellar streams in the galactic halo. This method is based on the GC3 method originally devised by Johnston, Hernquist, & Bolte (1996), modified to include velocity information in order to enhance the contrast of stream signatures with respect to the galactic halo background. We present our results on the efficiency of mGC3, tested by embedding tidal streams from N-body simulations in a mock Gaia catalogue of the galactic background, which includes a realistic realization of the photometric and kinematic properties, errors and completeness limits. We investigate mGC3's efficiency as a function of initial satellite luminosity, star formation history and orbital parameters and find that satellites in the range 10^8-10^9 L_⊙ can be recovered for streams as dynamically old as ~10 Gyr and up to galactocentric distances of ~40 kpc. For some combinations of dynamical ages and orbits, tidal streams with luminosities down to 4-5×10^7 L_⊙ can be recovered.

  19. Constraining the halo mass function with observations

    NASA Astrophysics Data System (ADS)

    Castro, Tiago; Marra, Valerio; Quartin, Miguel

    2016-12-01

    The abundances of dark matter haloes in the universe are described by the halo mass function (HMF). It enters most cosmological analyses and parametrizes how the linear growth of primordial perturbations is connected to these abundances. Interestingly, this connection can be made approximately cosmology independent. This made it possible to map in detail its near-universal behaviour through large-scale simulations. However, such simulations may suffer from systematic effects, especially if baryonic physics is included. In this paper, we ask how well observations can constrain directly the HMF. The observables we consider are galaxy cluster number counts, galaxy cluster power spectrum and lensing of Type Ia supernovae. Our results show that Dark Energy Survey is capable of putting the first meaningful constraints on the HMF, while both Euclid and J-PAS (Javalambre-Physics of the Accelerated Universe Astrophysical Survey) can give stronger constraints, comparable to the ones from state-of-the-art simulations. We also find that an independent measurement of cluster masses is even more important for measuring the HMF than for constraining the cosmological parameters, and can vastly improve the determination of the HMF. Measuring the HMF could thus be used to cross-check simulations and their implementation of baryon physics. It could even, if deviations cannot be accounted for, hint at new physics.

  20. Stellar Streams in the Andromeda Halo

    NASA Astrophysics Data System (ADS)

    Fardal, Mark A.; PAndAS Collaboration

    2011-05-01

    The PAndAS survey detects RGB and AGB stars in our neighbor galaxy M31, out to 150 kpc from the galaxy center with an extension to M33. Maps of this survey display a spectacular collection of stellar streams extending tens to hundreds of kpc in length. Many of these streams overlap with each other or with M31's central regions, making it difficult to disentangle the different streams. I discuss what is currently known about the nature, origin, significance, and eventual fate of these stellar streams. Photometric observations from the PAndAS survey and follow-up work constrain the metallicity, age, luminosity, and stellar mass of the stellar population. I discuss scenarios for how some of these streams formed, while for others their origin remains a mystery. I present observationally constrained numerical simulations for the formation of some of the streams. The streams also are probes of the mass profile and lumpiness of M31's dark matter halo. Spectroscopic samples are used to constrain M31's halo mass at large radius.

  1. Simulating the carbon footprint of galactic haloes

    NASA Astrophysics Data System (ADS)

    Bird, Simeon; Rubin, Kate H. R.; Suresh, Joshua; Hernquist, Lars

    2016-10-01

    We compare simulations, including the Illustris simulations, to observations of C IV and C II absorption at z = 2-4. These are the C IV column density distribution function in the column density range 1012-1015 cm-2, the C IV equivalent width distribution at 0.1-2 Å, and the covering fractions and equivalent widths of C IV1548 Å and C II 1337 Å around damped Lyman α systems (DLAs). In the context of the feedback models that we investigate, all C IV observations favour the use of more energetic wind models, which are better able to enrich the gas surrounding haloes. We propose two ways to achieve this: an increased wind velocity and an increase in wind thermal energy. However, even our most energetic wind models do not produce enough absorbers with C IV equivalent width >0.6 Å, which in our simulations are associated with the most massive haloes. All simulations are in reasonable agreement with the C II covering fraction and equivalent widths around damped Lyman α absorbers, although there is a moderate deficit in one bin 10-100 kpc from the DLA. Finally, we show that the C IV in our simulations is predominantly photoionized.

  2. Dictionary of Braille Music Signs.

    ERIC Educational Resources Information Center

    Krolick, Bettye

    This dictionary gathers into a single resource definitions of braille music signs used since 1888 and provides explanations of the wide variety of formats in which these signs have been used at different times by publishers around the world. More than 400 music signs and approximately 100 literary abbreviations are included, but musical terms are…

  3. Quine and the Segregrational Sign.

    ERIC Educational Resources Information Center

    Wolf, George

    1999-01-01

    In the context of theory of integrational linguistics, the segregational sign is distinguished from the integrational sign, and the operation of the former is analyzed. Focus is on how logic guides the sign, and how the theory of W. V. Quine accounts for these issues. (MSE)

  4. 3 CFR - Presidential Signing Statements

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... issued statements addressing constitutional or other legal questions upon signing bills into law (signing statements). Particularly since omnibus bills have become prevalent, signing statements have often been used... veto of the entire bill. In recent years, there has been considerable public discussion and criticism...

  5. Kinship in Mongolian Sign Language

    ERIC Educational Resources Information Center

    Geer, Leah

    2011-01-01

    Information and research on Mongolian Sign Language is scant. To date, only one dictionary is available in the United States (Badnaa and Boll 1995), and even that dictionary presents only a subset of the signs employed in Mongolia. The present study describes the kinship system used in Mongolian Sign Language (MSL) based on data elicited from…

  6. Kinship in Mongolian Sign Language

    ERIC Educational Resources Information Center

    Geer, Leah

    2011-01-01

    Information and research on Mongolian Sign Language is scant. To date, only one dictionary is available in the United States (Badnaa and Boll 1995), and even that dictionary presents only a subset of the signs employed in Mongolia. The present study describes the kinship system used in Mongolian Sign Language (MSL) based on data elicited from…

  7. Manual signing in adults with intellectual disability: influence of sign characteristics on functional sign vocabulary.

    PubMed

    Meuris, Kristien; Maes, Bea; De Meyer, Anne-Marie; Zink, Inge

    2014-06-01

    The purpose of this study was to investigate the influence of sign characteristics in a key word signing (KWS) system on the functional use of those signs by adults with intellectual disability (ID). All 507 signs from a Flemish KWS system were characterized in terms of phonological, iconic, and referential characteristics. Phonological and referential characteristics were assigned to the signs by speech-language pathologists. The iconicity (i.e., transparency, guessing the meaning of the sign; and translucency, rating on a 6-point scale) of the signs were tested in 467 students. Sign functionality was studied in 119 adults with ID (mean mental age of 50.54 months) by means of a questionnaire, filled out by a support worker. A generalized linear model with a negative binomial distribution (with log-link) showed that semantic category was the factor with the strongest influence on sign functionality, with grammatical class, referential concreteness, and translucency also playing a part. No sign phonological characteristics were found to be of significant influence on sign use. The meaning of a sign is the most important factor regarding its functionality (i.e., whether a sign is used in everyday communication). Phonological characteristics seem only of minor importance.

  8. STATISTICS OF DARK MATTER HALOS FROM THE EXCURSION SET APPROACH

    SciTech Connect

    Lapi, A.; Salucci, P.; Danese, L.

    2013-08-01

    We exploit the excursion set approach in integral formulation to derive novel, accurate analytic approximations of the unconditional and conditional first crossing distributions for random walks with uncorrelated steps and general shapes of the moving barrier; we find the corresponding approximations of the unconditional and conditional halo mass functions for cold dark matter (DM) power spectra to represent very well the outcomes of state-of-the-art cosmological N-body simulations. In addition, we apply these results to derive, and confront with simulations, other quantities of interest in halo statistics, including the rates of halo formation and creation, the average halo growth history, and the halo bias. Finally, we discuss how our approach and main results change when considering random walks with correlated instead of uncorrelated steps, and warm instead of cold DM power spectra.

  9. SUBSTRUCTURE IN THE STELLAR HALOS OF THE AQUARIUS SIMULATIONS

    SciTech Connect

    Helmi, Amina; Cooper, A. P.; Cole, S.; Frenk, C. S.; White, S. D. M.; Navarro, J. F.

    2011-05-20

    We characterize the substructure in the simulated stellar halos of Cooper et al. which were formed by the disruption of satellite galaxies within the cosmological N-body simulations of galactic halos of the Aquarius project. These stellar halos exhibit a wealth of tidal features: broad overdensities and very narrow faint streams akin to those observed around the Milky Way. The substructures are distributed anisotropically on the sky, a characteristic that should become apparent in the next generation of photometric surveys. The normalized RMS of the density of stars on the sky appears to be systematically larger for our halos compared with the value estimated for the Milky Way from main-sequence turnoff stars in the Sloan Digital Sky Survey. We show that this is likely to be due in part to contamination by faint QSOs and redder main-sequence stars, and might suggest that {approx}10% of the Milky Way halo stars have formed in situ.

  10. Observations of diffusion in the electron halo and strahl

    NASA Astrophysics Data System (ADS)

    Gurgiolo, Chris; Goldstein, Melvyn L.

    2016-12-01

    Observations of the three-dimensional solar wind electron velocity distribution functions (VDF) using ϕ-θ plots often show a tongue of electrons that begins at the strahl and stretches toward a new population of electrons, termed the proto-halo, that exists near the projection of the magnetic field opposite that associated with the strahl. The energy range in which the tongue and proto-halo are observed forms a "diffusion zone". The tongue first appears in energy generally near the lower-energy range of the strahl and in the absence of any clear core/halo signature. While the ϕ-θ plots give the appearance that the tongue and proto-halo are derived from the strahl, a close examination of their density suggests that their source is probably the upper-energy core/halo electrons which have been scattered by one or more processes into these populations.

  11. A halo and a blow-out in NGC 253

    NASA Technical Reports Server (NTRS)

    Carilli, C. L.; Holdaway, M. A.; Ho, P. T. P.

    1993-01-01

    We present the discovery of a 'synchrotron halo' in NGC 253. NGC 253 is an inclined, dusty, barred Sc galaxy in the Sculptor Group. It is also one of the prototype nuclear star burst galaxies. Very Large Array observations at 327 MHz and 1.4 GHz have revealed a synchrotron emitting 'halo' extending 9 kpc above and below the plane of NGC 253 (assuming a distance of 4 Mpc). The spectral index for the radio emission steepens from -0.7 in the disk to -1.0 in the halo. The fractional polarization at 1.4 GHz increases from less than or equal to 2 percent in the disk up to 20 percent in the halo, and the magnetic field vectors project parallel to the plane over most of the halo.

  12. Recurrent dislocations of the atlantooccipital and atlantoaxial joints in a halo vest fixator are resolved by backrest elevation in an elevation angle-dependent manner.

    PubMed

    Kato, Go; Kawaguchi, Kenichi; Tsukamoto, Nobuaki; Komiyama, Keisuke; Mizuta, Kazutaka; Onohara, Takayuki; Okano, Hirofumi; Hotokezaka, Shunsuke; Mae, Takao

    2015-10-01

    Halo fixation is now universally performed in the initial reduction and fixation of unstable upper cervical spine injuries; however, persistent high instability and recurrent dislocations of the atlantooccipital and atlantoaxial joints after fixation are not well recognized. The aim was to describe persistent instability of traumatic dislocations of the atlantooccipital and atlantoaxial joints after halo fixation and a useful method for preventing instability. This was a case report of a patient who survived traumatic dislocations of the atlantooccipital and atlantoaxial joints. A 73-year-old woman diagnosed with dislocations of the atlantooccipital and atlantoaxial joints along with multiple other injuries sustained in a traffic accident was included. After initial closed reduction and halo fixation, congruity of the atlantooccipital and atlantoaxial joints was evaluated using, condylar gap, atlantodental interval, and flexion angulation of C1-C2 after the initial examination and before surgery. Changes in parameters 12 hours after halo fixation revealed re-dislocations and instability of the joints. Backrest elevation with halo fixation tended to reduce re-dislocations. Therefore, we carefully increased the backrest angle and measured the parameters at several angles of elevation within a range that did not affect vital signs to observe the effectiveness of elevation against re-dislocations. Elevation changed the parameters in an elevation angle-dependent manner, and these changes suggested that elevation was effective for reducing re-dislocation of both the atlantooccipital and atlantoaxial joints during halo fixation. With no major complications, this method enabled us to maintain good congruity of the joints for approximately 2 weeks until posterior spinal fusion with internal fixation. Backrest elevation with halo fixation appears safe to be performed without any other devices and is beneficial for blocking re-dislocation of both the atlantooccipital and

  13. Binary white dwarfs in the halo of the Milky Way

    NASA Astrophysics Data System (ADS)

    van Oirschot, Pim; Nelemans, Gijs; Toonen, Silvia; Pols, Onno; Brown, Anthony G. A.; Helmi, Amina; Portegies Zwart, Simon

    2014-09-01

    Aims: We study single and binary white dwarfs in the inner halo of the Milky Way in order to learn more about the conditions under which the population of halo stars was born, such as the initial mass function (IMF), the star formation history, or the binary fraction. Methods: We simulate the evolution of low-metallicity halo stars at distances up to ~3 kpc using the binary population synthesis code SeBa. We use two different white dwarf cooling models to predict the present-day luminosities of halo white dwarfs. We determine the white dwarf luminosity functions (WDLFs) for eight different halo models and compare these with the observed halo WDLF of white dwarfs in the SuperCOSMOS Sky Survey. Furthermore, we predict the properties of binary white dwarfs in the halo and determine the number of halo white dwarfs that is expected to be observed with the Gaia satellite. Results: By comparing the WDLFs, we find that a standard IMF matches the observations more accurately than a top-heavy one, but the difference with a bottom-heavy IMF is small. A burst of star formation 13 Gyr ago fits slightly better than a star formation burst 10 Gyr ago and also slightly better than continuous star formation 10-13 Gyr ago. Gaia will be the first instument to constrain the bright end of the field halo WDLF, where contributions from binary WDs are considerable. Many of these will have He cores, of which a handful have atypical surface gravities (log g < 6) and reach luminosities log (L/L⊙) > 0 in our standard model for WD cooling. These so called pre-WDs, if observed, can help us to constrain white dwarf cooling models and might teach us something about the fraction of halo stars that reside in binaries. Appendices are available in electronic form at http://www.aanda.org

  14. Kinematic imprint of clumpy disk formation on halo objects

    NASA Astrophysics Data System (ADS)

    Inoue, Shigeki

    2013-02-01

    Context. Clumpy disk galaxies in the distant universe, at redshift of z ≳ 1, have been observed to host several giant clumps in their disks. They are thought to correspond to early formative stages of disk galaxies. On the other hand, halo objects, such as old globular clusters and halo stars, are likely to consist of the oldest stars in a galaxy (age ≳ 10 Gyr), clumpy disk formation can thus be presumed to take place in a pre-existing halo system. Aims: Giant clumps orbit in the same direction in a premature disk and are so massive that they may be expected to interact gravitationally with halo objects and exercise influence on the kinematic state of the halo. Accordingly, I scrutinize the possibility that the clumps leave a kinematic imprint of the clumpy disk formation on a halo system. Methods: I perform a restricted N-body calculation with a toy model to study the kinematic influence on a halo by orbital motions of clumps and the dependence of the results on masses (mass loss), number, and orbital radii of the clumps. Results: I show that halo objects can catch clump motions and acquire disky rotation in a dynamical friction time scale of the clumps, ~0.5 Gyr. The influence of clumps is limited within a region around the disk, while the halo system shows vertical gradients of net rotation velocity and orbital eccentricity. The significance of the kinematic influence strongly depends on the clump masses; the lower limit of postulated clump mass would be ~5 × 108 M⊙. The result also depends on whether the clumps are subjected to rapid mass loss or not, which is an open question under debate in recent studies. The existence of such massive clumps is not unrealistic. I therefore suggest that the imprints of past clumpy disk formation could remain in current galactic halos.

  15. The Origin of Angular Momentum in Dark Matter Halos

    NASA Astrophysics Data System (ADS)

    Vitvitska, Maya; Klypin, Anatoly A.; Kravtsov, Andrey V.; Wechsler, Risa H.; Primack, Joel R.; Bullock, James S.

    2002-12-01

    We propose a new explanation for the origin of angular momentum in galaxies and their dark halos, in which the halos obtain their spin through the cumulative acquisition of angular momentum from satellite accretion. In our model, the buildup of angular momentum is a random walk process associated with the mass assembly history of the halo's major progenitor. We assume no correlation between the angular momenta of accreted objects. The main role of tidal torques in this approach is to produce the random tangential velocities of merging satellites. Using the extended Press-Schechter approximation, we calculate the growth of mass, angular momentum, and spin parameter λ for many halos. Our random walk model reproduces the key features of the angular momentum of halos found in ΛCDM N-body simulations: a lognormal distribution in λ with an average of <λ>~0.045 and dispersion σλ=0.56, independent of mass and redshift. The evolution of the spin parameter in individual halos in this model is quite different from the steady increase with time of angular momentum in the tidal torque picture. We find both in N-body simulations and in our random walk model that the value of λ changes significantly with time for a halo's major progenitor. It typically has a sharp increase due to major mergers and a steady decline during periods of gradual accretion of small satellites. The model predicts that, on average, the λ of ~1012 Msolar halos that had major mergers after redshift z=3 should be substantially larger than the λ of those that did not. Perhaps surprisingly, this suggests that halos that host later forming elliptical galaxies should rotate faster than halos of spiral galaxies.

  16. Mapping the Galactic Halo. I. The ``Spaghetti'' Survey

    NASA Astrophysics Data System (ADS)

    Morrison, Heather L.; Mateo, Mario; Olszewski, Edward W.; Harding, Paul; Dohm-Palmer, R. C.; Freeman, Kenneth C.; Norris, John E.; Morita, Miwa

    2000-05-01

    We describe a major survey of the Milky Way halo designed to test for kinematic substructure caused by destruction of accreted satellites. We use the Washington photometric system to identify halo stars efficiently for spectroscopic follow-up. Tracers include halo giants (detectable out to more than 100 kpc), blue horizontal-branch (BHB) stars, halo stars near the main-sequence turnoff, and the ``blue metal-poor stars'' of Preston, Beers, & Shectman. We demonstrate the success of our survey by showing spectra of stars we have identified in all these categories, including giants as distant as 75 kpc. We discuss the problem of identifying the most distant halo giants. In particular, extremely metal-poor halo K dwarfs are present in approximately equal numbers to the distant giants for V>18, and we show that our method will distinguish reliably between these two groups of metal-poor stars. We plan to survey 100 deg2 at high Galactic latitude and expect to increase the numbers of known halo giants, BHB stars, and turnoff stars by more than an order of magnitude. In addition to the strong test that this large sample will provide for the question, Was the Milky Way halo accreted from satellite galaxies? we will improve the accuracy of mass measurements of the Milky Way beyond 50 kpc via the kinematics of the many distant giants and BHB stars we find. We show that one of our first data sets constrains the halo density law over Galactocentric radii of 5-20 kpc and z-heights of 2-15 kpc. The data support a flattened power-law halo with b/a of 0.6 and exponent -3.0. More complex models with a varying axial ratio may be needed with a larger data set.

  17. Zooming in on accretion - I. The structure of halo gas

    NASA Astrophysics Data System (ADS)

    Nelson, Dylan; Genel, Shy; Pillepich, Annalisa; Vogelsberger, Mark; Springel, Volker; Hernquist, Lars

    2016-08-01

    We study the properties of gas in and around 1012 M⊙ haloes at z = 2 using a suite of high-resolution cosmological hydrodynamic `zoom' simulations. We quantify the thermal and dynamical structure of these gaseous reservoirs in terms of their mean radial distributions and angular variability along different sightlines. With each halo simulated at three levels of increasing resolution, the highest reaching a baryon mass resolution of ˜10 000 solar masses, we study the interface between filamentary inflow and the quasi-static hot halo atmosphere. We highlight the discrepancy between the spatial resolution available in the halo gas as opposed to within the galaxy itself, and find that stream morphologies become increasingly complex at higher resolution, with large coherent flows revealing density and temperature structure at progressively smaller scales. Moreover, multiple gas components co-exist at the same radius within the halo, making radially averaged analyses misleading. This is particularly true where the hot, quasi-static, high entropy halo atmosphere interacts with cold, rapidly inflowing, low entropy accretion. Haloes at this mass have a well-defined virial shock, associated with a sharp jump in temperature and entropy at ≳ 1.25 rvir. The presence, radius, and radial width of this boundary feature, however, vary not only from halo to halo, but also as a function of angular direction, covering roughly ˜75 per cent of the 4π sphere. We investigate the process of gas virialization as imprinted in the halo structure, and discuss different modes for the accretion of gas from the intergalactic medium.

  18. HALO384: a halo-based potency prediction algorithm for high-throughput detection of antimicrobial agents.

    PubMed

    Woehrmann, Marcos H; Gassner, Nadine C; Bray, Walter M; Stuart, Joshua M; Lokey, Scott

    2010-02-01

    A high-throughput (HT) agar-based halo assay is described, which allows for rapid screening of chemical libraries for bioactivity in microorganisms such as yeast and bacteria. A pattern recognition algorithm was developed to identify halo-like shapes in plate reader optical density (OD) measurements. The authors find that the total growth inhibition within a detected halo provides an accurate estimate of a compound's potency measured in terms of its EC(50). The new halo recognition method performs significantly better than an earlier method based on single-point OD readings. An assay based on the halo algorithm was used to screen a 21,120-member library of drug-like compounds in Saccharomyces cerevisiae, leading to the identification of novel bioactive scaffolds containing derivatives of varying potencies. The authors also show that the HT halo assay can be performed with the pathogenic bacterium Vibrio cholerae and that liquid culture EC(50) values and halo scores show a good correlation in this organism. These results suggest that the HT halo assay provides a rapid and inexpensive way to screen for bioactivity in multiple microorganisms.

  19. [The Einstein sign].

    PubMed

    Treska, V

    2003-02-01

    Untreated rupture of an aneurysm of the abdominal aorta is fatal in almost 100% of the patients. In the majority of cases the assessment of a correct, early diagnosis is simple (hypotension, backache, abdominal pain, pulsating resistance in the abdomen) and makes a prompt surgical or endovascular operation possible. In some instances however rupture of aneurysms of the abdominal aorta simulates other clinical conditions (acute cholecystitis, acute diverculitis of the sigmoid) which may delay the correct diagnosis and reduce the patient's chance of survival. The author describes, based on historical documents, the treacherous course of the disease in the scientific genius Albert Einstein where rupture of an aneurysm simulated acute cholecystitis, and in the world literature this symptomatology was subsequently described as Einstein's sign.

  20. [Halos and multifocal intraocular lenses: origin and interpretation].

    PubMed

    Alba-Bueno, F; Vega, F; Millán, M S

    2014-10-01

    To present the theoretical and experimental characterization of the halo in multifocal intraocular lenses (MIOL). The origin of the halo in a MIOL is the overlaying of 2 or more images. Using geometrical optics, it can be demonstrated that the diameter of each halo depends on the addition of the lens (ΔP), the base power (P(d)), and the diameter of the IOL that contributes to the «non-focused» focus. In the image plane that corresponds to the distance focus, the halo diameter (δH(d)) is given by: δH(d)=d(pn) ΔP/P(d), where d(pn) is the diameter of the IOL that contributes to the near focus. Analogously, in the near image plane the halo diameter (δH(n)) is: δH(n)=d(pd) ΔP/P(d), where d(pd) is the diameter of the IOL that contributes to the distance focus. Patients perceive halos when they see bright objects over a relatively dark background. In vitro, the halo can be characterized by analyzing the intensity profile of the image of a pinhole that is focused by each of the foci of a MIOL. A comparison has been made between the halos induced by different MIOL of the same base power (20D) in an optical bench. As predicted by theory, the larger the addition of the MIOL, the larger the halo diameter. For large pupils and with MIOL with similar aspheric designs and addition (SN6AD3 vs ZMA00), the apodized MIOL has a smaller halo diameter than a non-apodized one in distance vision, while in near vision the size is very similar, but the relative intensity is higher in the apodized MIOL. When comparing lenses with the same diffractive design, but with different spherical-aspheric base design (SN60D3 vs SN6AD3), the halo in distance vision of the spherical MIOL is larger, while in near vision the spherical IOL induces a smaller halo, but with higher intensity due to the spherical aberration of the distance focus in the near image. In the case of a trifocal-diffractive IOL (AT LISA 839MP) the most noticeable characteristic is the double-halo formation due to the 2 non

  1. The Making of the Milky Way Halo

    NASA Astrophysics Data System (ADS)

    1999-02-01

    The VLT Watches a Dissolving Stellar Cluster A group of ESO astronomers [1] has used new observations, obtained with the first 8.2-m VLT Unit Telescope (UT1) during the "Science Verification" programme, to show that a globular cluster in the Milky Way galaxy is "evaporating" and has already lost its faintest stars. This is the first observational result of its kind and has important implications for future studies. It may be explained by a gradual loss of such stars from the cluster into the Milky Way halo, a roughly spherical region around the much flatter, spiral structure in which most of the stars and nebulae are located. The new result lends strong support to current theories about the evolution of the structure of this halo and also provides insights into the formation of the galaxy in which we live. Globular clusters and the halo of the Milky Way The stars that we observe in the halo of the Milky Way represent only a small fraction of the total mass in this region. Investigations of the motions of stars in our Galaxy have shown that this halo must harbour much more matter, which is hidden from our view. The same phenomenon has been observed in other galaxies, and astronomers refer to it as "dark matter". It is at this moment not known what this matter consists of. The brightest objects in the halo are the globular clusters . They are large groupings of stars that were formed together in the very early evolutionary phases of the Milky Way, some 12,000 - 14,000 million years ago. This happened soon after the moment when the first structures emerged in the large cloud of primordial hydrogen in which our Galaxy was born. A popular scenario describes the first build-up of galactic structure, i.e. of stars and gas, as when normal matter began to collect inside the dark-matter halo, due to its strong gravitational attraction. The globular clusters were most probably the first denizens of this protogalaxy . It is believed that the Milky Way Galaxy subsequently

  2. Ergonomics and design: traffic sign and street name sign.

    PubMed

    Moroni, Janaina Luisa da Silva; Aymone, José Luís Farinatti

    2012-01-01

    This work proposes a design methodology using ergonomics and anthropometry concepts applied to traffic sign and street name sign projects. Initially, a literature revision on cognitive ergonomics and anthropometry is performed. Several authors and their design methodologies are analyzed and the aspects to be considered in projects of traffic and street name signs are selected and other specific aspects are proposed for the design methodology. A case study of the signs of "Street of Antiques" in Porto Alegre city is presented. To do that, interviews with the population are made to evaluate the current situation of signs. After that, a new sign proposal with virtual prototyping is done using the developed methodology. The results obtained with new interviews about the proposal show the user satisfaction and the importance of cognitive ergonomics to development of this type of urban furniture.

  3. Sign language comprehension: the case of Spanish sign language.

    PubMed

    Rodríguez Ortiz, I R

    2008-01-01

    This study aims to answer the question, how much of Spanish Sign Language interpreting deaf individuals really understand. Study sampling included 36 deaf people (deafness ranging from severe to profound; variety depending on the age at which they learned sign language) and 36 hearing people who had good knowledge of sign language (most were interpreters). Sign language comprehension was assessed using passages of secondary level. After being exposed to the passages, the participants had to tell what they had understood about them, answer a set of related questions, and offer a title for the passage. Sign language comprehension by deaf participants was quite acceptable but not as good as that by hearing signers who, unlike deaf participants, were not only late learners of sign language as a second language but had also learned it through formal training.

  4. The mass transfer kinetics in columns packed with Halo-ES shell particles.

    PubMed

    Gritti, Fabrice; Guiochon, Georges

    2011-02-18

    The average mesopore size of the new Halo-ES-Peptide shell particles is 160 Å, markedly larger than that of the classical Halo shell particles (90 Å). We found that this change causes a considerable decrease of the film mass transfer resistance measured for columns packed with these particles. We analyze data obtained by systematic measurements of the C term of the van Deemter equation for the peptide β-lipotropin (MW = 769 Da), the protein insulin (MW = 5800 Da), and a series of non-retained polystyrene standards (MW = 6400 and 13,200). The improvement in column performance is explained by an increase of the fraction of the external surface area of the shell that allows the entrance of the sample molecules inside the particle. The fraction of the shell surface accessible to a probe controls the rate of its external film mass transfer, i.e. its rate of transfer between the interstitial and the stagnant eluent. Although measurable, the increase in sample diffusivity through the porous shells does not account for the better performance of Halo-ES-peptide columns. Furthermore, the analysis of the HETPs data of small molecules (uracil, acetophenone, toluene, and naphthalene, MW< 150) reveals that the eddy diffusion (A) term of these new columns is 25% lower than that of the classical Halo columns. This result is consistent with the impact of intra-particle diffusivity on the eddy diffusion mechanism in packed columns. As shell diffusivity increases, so does the rate of transfer of sample molecules between the eluent stream-paths flowing through the packed particles and across the column diameter. Dispersion through short-range inter-channel and trans-column eddies is reduced. Copyright © 2010 Elsevier B.V. All rights reserved.

  5. Sign reversal of the Hall resistivity of single-crystalline Bi{sub 1.95}Sr{sub 1.65}La{sub 0.4}CuO{sub 6+{delta}} and Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}}

    SciTech Connect

    Jin, R.; Ott, H.R.

    1996-04-01

    The Hall effect of single-crystalline Bi{sub 2}Sr{sub 2}CaCu{sub 2}O{sub 8+{delta}} and Bi{sub 1.95}Sr{sub 1.65}La{sub 0.4}CuO{sub 6+{delta}} has been measured above and below the superconducting transition temperature {ital T}{sub {ital c}0} by applying magnetic fields {bold H}{parallel}{ital c} and currents {ital I}{perpendicular}{ital c}, where {ital c} denotes the direction perpendicular to the Cu-O planes of these materials. For both compounds, the Hall resistivity {rho}{sub {ital xy}}({ital T},{bold H}) reveals similar temperature and field dependences. As {ital T} approaches {ital T}{sub {ital c}0} from higher temperatures, the {rho}{sub {ital xy}}({ital T},{bold H}) versus {bold H} curves gradually deviate from linearity and exhibit an unusual sign reversal in the low-field regime. The total Hall resistivity {rho}{sub {ital xy}}({ital T},{bold H}) may be decomposed into three distinctly different terms, i.e., {rho}{sub {ital xy}}({ital T},{ital H})={rho}{sub {ital xy}}{sup 0}({ital T})+{ital R}{sub {ital H}}{sup {prime}}({ital T}) H{ital H}+{rho}{sub {ital xy}}{sup {ital x}}({ital T},{ital H}). The contribution {rho}{sup {ital x}}{sub {ital xy}}({ital T},{bold H}), representing the deviation of {rho}{sub {ital xy}}({ital T},{bold H}) from {bold H} linearity, exhibits a universal scaling behavior as a function of {bold H}/{bold H}{sub 0}({ital T}) for fields between 0 and {bold H}{sub 0}({ital T}), the field below which {rho}{sub {ital xy}}({ital T},{bold H}) is no longer linear in {bold H}. {copyright} {ital 1996 The American Physical Society.}

  6. Evaluation and evolution of speed for halo and partial halo CMEs

    NASA Astrophysics Data System (ADS)

    Becerril, Carlos; Muñoz Martínez, Guadalupe; Lopez-Lopez, Jose Luis

    Halo CMEs are known to be directed towards the Earth; and therefore are of great interest in space weather forecasting. Two main issues are involved in making good arrival predictions: the precision of the evaluation of the initial parameters near the Sun and an appropriate model for ICME propagation. The initial CME speed and direction are needed to infer the travel time, but these crucial parameters are difficult to obtain for earthward pointed CMEs. In this work we identified halo and partial halo CMES associated to EIT flares and Interplanetary Shocks. Considering the location of the flare and the projection effect we evaluated the initial speed of the CME; using the initial values we calculated the arrival time and speed and compared these values to the ones of the ICME related. We found a good approximation to the actual parameters, showing that the models applied in the evaluation of the initial parameters and the prediction of the final ones are consistent to the real evolution of the phenomena.

  7. Inhomogeneous chemical enrichment in the Galactic Halo

    NASA Astrophysics Data System (ADS)

    Kobayashi, Chiaki

    2015-08-01

    In a galaxy, chemical enrichment takes place in an inhomogeneous fashion, and the Galactic Halo is one of the places where the inhomogeneous effects are imprinted and can be constrained from observations. I show this using my chemodynamical simulations of Milky Way type galaxies. The scatter in the elemental abundances is originated from radial migration, merging/accretion of satellite galaxies, local variation of star formation and chemical enrichment, and intrinsic variation of nucleosynthesis yields. In the simulated galaxies, there is no strong age-metallicity relations. This means that the most metal poor stars are not always the oldest stars, and can be formed in chemically unevolved clouds at later times. The long-lifetime sources of chemical enrichment such as asymptotic giant blanch stars or neutron star mergers can contribute the abundance patterns of extremely metal-poor stars, which are in good agreement with observations.

  8. Jupiter's Main Ring/Ring Halo

    NASA Technical Reports Server (NTRS)

    1997-01-01

    A mosaic of four images taken through the clear filter (610 nanometers) of the solid state imaging (CCD) system aboard NASA's Galileo spacecraft on November 8, 1996, at a resolution of approximately 46 kilometers (28.5 miles) per picture element (pixel) along Jupiter's rings. Because the spacecraft was only about 0.5 degrees above the ring plane, the image is highly foreshortened in the vertical direction. The images were obtained when Galileo was in Jupiter's shadow, peering back toward the Sun; the ring was approximately 2.3 million kilometers (1.4 million miles) away. The arc on the far right of the image is produced when sunlight is scattered by small particles comprising Jupiter's upper atmospheric haze. The ring also efficiently scatters light, indicating that much of its brightness is due to particles that are microns or less in diameter. Such small particles are believed to have human-scale lifetimes, i.e., very brief compared to the solar system's age.

    Jupiter's ring system is composed of three parts - - a flat main ring, a lenticular halo interior to the main ring, and the gossamer ring, outside the main ring. The near and far arms of Jupiter's main ring extend horizontally across the mosaic, joining together at the ring's ansa, on the figure's far left side. The near arm of the ring appears to be abruptly truncated close to the planet, at the point where it passes into Jupiter's shadow. Some radial structure is barely visible across the ring's ansa (top image). A faint mist of particles can be seen above and below the main rings. This vertically extended 'halo' is unusual in planetary rings, and is probably caused by electromagnetic forces pushing the smallest grains out of the ring plane. Because of shadowing, the halo is not visible close to Jupiter in the lower right part of the mosaic. To accentuate faint features in the bottom image of the ring halo, different brightnesses are shown through color. Brightest features are white or yellow and the

  9. Jupiter's Main Ring/Ring Halo

    NASA Technical Reports Server (NTRS)

    1997-01-01

    A mosaic of four images taken through the clear filter (610 nanometers) of the solid state imaging (CCD) system aboard NASA's Galileo spacecraft on November 8, 1996, at a resolution of approximately 46 kilometers (28.5 miles) per picture element (pixel) along Jupiter's rings. Because the spacecraft was only about 0.5 degrees above the ring plane, the image is highly foreshortened in the vertical direction. The images were obtained when Galileo was in Jupiter's shadow, peering back toward the Sun; the ring was approximately 2.3 million kilometers (1.4 million miles) away. The arc on the far right of the image is produced when sunlight is scattered by small particles comprising Jupiter's upper atmospheric haze. The ring also efficiently scatters light, indicating that much of its brightness is due to particles that are microns or less in diameter. Such small particles are believed to have human-scale lifetimes, i.e., very brief compared to the solar system's age.

    Jupiter's ring system is composed of three parts - - a flat main ring, a lenticular halo interior to the main ring, and the gossamer ring, outside the main ring. The near and far arms of Jupiter's main ring extend horizontally across the mosaic, joining together at the ring's ansa, on the figure's far left side. The near arm of the ring appears to be abruptly truncated close to the planet, at the point where it passes into Jupiter's shadow. Some radial structure is barely visible across the ring's ansa (top image). A faint mist of particles can be seen above and below the main rings. This vertically extended 'halo' is unusual in planetary rings, and is probably caused by electromagnetic forces pushing the smallest grains out of the ring plane. Because of shadowing, the halo is not visible close to Jupiter in the lower right part of the mosaic. To accentuate faint features in the bottom image of the ring halo, different brightnesses are shown through color. Brightest features are white or yellow and the

  10. The optical halo around NGC 253

    NASA Astrophysics Data System (ADS)

    Beck, R.; Hutschenreiter, G.; Wielebinski, R.

    1982-02-01

    A photographic technique of image enhancement and digital smoothing of P.D.S. scans are used to study the blue light from an extended halo surrounding NGC 253. The photographic technique, described by Malin (1978), is based on the fact that the true image is formed in the topmost surface layer of the emission of a plate, while the fog is found in deeper layers of the emulsion. The investigation made it possible to follow the distribution of light out to 10 kpc from the plane of the galaxy. Synchrotron emission is responsible for the bulk of radio continuum emission in NGC 253 (Beck et al., 1979). Moreover, the radio map at a wavelength of 3.4 cm shows a spur-like feature at the exact position where the diffuse loop of light is seen, indicating a similar emission origin.

  11. The Extent of Hot Gaseous Galaxy Halos

    NASA Astrophysics Data System (ADS)

    Bregman, Joel N.; Anderson, Michael E.; Hodges-Kluck, Edmund J.; Miller, Matthew J.; Dai, Xinyu

    2017-01-01

    There are several constraints on the hot gas distribution around the Milky Way and external galaxies, but they are confined to within about 50 kpc, approximately 0.2R200. Beyond 0.2R200, several density distributions have been proposed, some that contain all the missing baryons within R200 and others that have the baryons extending to 2-3R200 before reaching the cosmological baryon to dark matter ratio. These differences are determined by galaxy formation processes and by feedback from supernovae and AGN. We present the conflicting evidence for the different extended baryon distributions. A clearer picture of the properties of these hot galaxy halos would be provided by high resolution soft X-ray spectroscopy, such as of the O VII and O VIII resonance lines, and the proposed Arcus mission would enable these breakthrough observations.

  12. Particle Dark Matter in the galactic halo

    NASA Astrophysics Data System (ADS)

    Bernabei, R.; Belli, P.; D'Angelo, S.; di Marco, A.; Montecchia, F.; D'Angelo, A.; Incicchitti, A.; Cappella, F.; Caracciolo, V.; Cerulli, R.; Dai, C. J.; He, H. L.; Kuang, H. H.; Ma, X. H.; Sheng, X. D.; Wang, R. G.; Ye, Z. P.

    2015-10-01

    The DAMA/LIBRA-phase1 and the former DAMA/NaI data (cumulative exposure 1.33 ton × yr, corresponding to 14 annual cycles) give evidence at 9.3σ C.L. for the presence of Dark Matter (DM) particles in the galactic halo, on the basis of the exploited model independent DM annual modulation signature by using highly radio-pure NaI(Tl) target. Results and comparisons will be shortly recalled. Recent analyses on possible diurnal effects and on the Earth shadowing effect (the latter holds only for some DM candidates) will be mentioned. The analysis of the time distribution of the low-energy single-hit events in DAMA/LIBRA-phase1 is reported for the first time. Finally, some perspectives of the presently running DAMA/LIBRA-phase2 will be mentioned.

  13. The slight spin of the old stellar halo

    NASA Astrophysics Data System (ADS)

    Deason, Alis J.; Belokurov, Vasily; Koposov, Sergey E.; Gómez, Facundo A.; Grand, Robert J.; Marinacci, Federico; Pakmor, Rüdiger

    2017-09-01

    We combine Gaia data release 1 astrometry with Sloan Digital Sky Survey (SDSS) images taken some ∼10-15 years earlier, to measure proper motions of stars in the halo of our Galaxy. The SDSS-Gaia proper motions have typical statistical errors of 2 mas yr-1 down to r ∼ 20 mag, and are robust to variations with magnitude and colour. Armed with this exquisite set of halo proper motions, we identify RR Lyrae, blue horizontal branch (BHB), and K giant stars in the halo, and measure their net rotation with respect to the Galactic disc. We find evidence for a gently rotating prograde signal (〈Vϕ〉 ∼ 5-25 km s-1) in the halo stars, which shows little variation with Galactocentric radius out to 50 kpc. The average rotation signal for the three populations is 〈Vϕ〉 = 14 ± 2 ± 10 (syst.) km s-1. There is also tentative evidence for a kinematic correlation with metallicity, whereby the metal richer BHB and K giant stars have slightly stronger prograde rotation than the metal poorer stars. Using the Auriga simulation suite, we find that the old (T >10 Gyr) stars in the simulated haloes exhibit mild prograde rotation, with little dependence on radius or metallicity, in general agreement with the observations. The weak halo rotation suggests that the Milky Way has a minor in situ halo component, and has undergone a relatively quiet accretion history.

  14. Optimal linear reconstruction of dark matter from halo catalogues

    DOE PAGES

    Cai, Yan -Chuan; Bernstein, Gary; Sheth, Ravi K.

    2011-04-01

    The dark matter lumps (or "halos") that contain galaxies have locations in the Universe that are to some extent random with respect to the overall matter distributions. We investigate how best to estimate the total matter distribution from the locations of the halos. We derive the weight function w(M) to apply to dark-matter haloes that minimizes the stochasticity between the weighted halo distribution and its underlying mass density field. The optimal w(M) depends on the range of masses of halos being used. While the standard biased-Poisson model of the halo distribution predicts that bias weighting is optimal, the simple factmore » that the mass is comprised of haloes implies that the optimal w(M) will be a mixture of mass-weighting and bias-weighting. In N-body simulations, the Poisson estimator is up to 15× noisier than the optimal. Optimal weighting could make cosmological tests based on the matter power spectrum or cross-correlations much more powerful and/or cost effective.« less

  15. Optimal linear reconstruction of dark matter from halo catalogues

    SciTech Connect

    Cai, Yan -Chuan; Bernstein, Gary; Sheth, Ravi K.

    2011-04-01

    The dark matter lumps (or "halos") that contain galaxies have locations in the Universe that are to some extent random with respect to the overall matter distributions. We investigate how best to estimate the total matter distribution from the locations of the halos. We derive the weight function w(M) to apply to dark-matter haloes that minimizes the stochasticity between the weighted halo distribution and its underlying mass density field. The optimal w(M) depends on the range of masses of halos being used. While the standard biased-Poisson model of the halo distribution predicts that bias weighting is optimal, the simple fact that the mass is comprised of haloes implies that the optimal w(M) will be a mixture of mass-weighting and bias-weighting. In N-body simulations, the Poisson estimator is up to 15× noisier than the optimal. Optimal weighting could make cosmological tests based on the matter power spectrum or cross-correlations much more powerful and/or cost effective.

  16. Solar wind halo electrons from 1-4 AU

    NASA Technical Reports Server (NTRS)

    Mccomas, D. J.; Bame, S. J.; Feldman, W. C.; Gosling, J. T.; Phillips, J. L.

    1992-01-01

    Observations from the Ulysses solar wind electron spectrometer are used to make a first examination of the evolution of the solar wind suprathermal or halo electron population as a function of heliocentric distance beyond 1 AU. As the core population cools with increasing heliocentric distance, no gap is formed between the core and halo populations. Rather, the halo electrons extend to increasingly lower energies. As predicted previously on theoretical grounds, the ratio of the core electron temperature to the low energy cutoff of the halo population appears to be roughly constant with a value of about 7.5. The total integrated heat flux drops rapidly with increasing heliocentric distance; a best fit power law of R exp -2.36 is found. In addition, it is found that the ratio of the halo to core densities is roughly constant over heliocentric distance with the halo representing 4 percent of the total electron distribution. These results suggest that the halo population may not consist of truly noninteractive test particles over the heliocentric range of 1-4 AU.

  17. Universal Dark Halo Scaling Relation for the Dwarf Spheroidal Satellites

    NASA Astrophysics Data System (ADS)

    Hayashi, Kohei; Ishiyama, Tomoaki; Ogiya, Go; Chiba, Masashi; Inoue, Shigeki; Mori, Masao

    2017-07-01

    Motivated by a recently found interesting property of the dark halo surface density within a radius, {r}\\max , giving the maximum circular velocity, {V}\\max , we investigate it for dark halos of the Milky Way’s and Andromeda’s dwarf satellites based on cosmological simulations. We select and analyze the simulated subhalos associated with Milky-Way-sized dark halos and find that the values of their surface densities, {{{Σ }}}{V\\max }, are in good agreement with those for the observed dwarf spheroidal satellites even without employing any fitting procedures. Moreover, all subhalos on the small scales of dwarf satellites are expected to obey the universal relation, irrespective of differences in their orbital evolutions, host halo properties, and observed redshifts. Therefore, we find that the universal scaling relation for dark halos on dwarf galaxy mass scales surely exists and provides us with important clues for understanding fundamental properties of dark halos. We also investigate orbital and dynamical evolutions of subhalos to understand the origin of this universal dark halo relation and find that most subhalos evolve generally along the {r}\\max \\propto {V}\\max sequence, even though these subhalos have undergone different histories of mass assembly and tidal stripping. This sequence, therefore, should be the key feature for understanding the nature of the universality of {{{Σ }}}{V\\max }.

  18. Characterization of Polar Mesospheric Clouds Using Infrared Measurements From HALOE

    NASA Technical Reports Server (NTRS)

    Hervig, Mark E.

    2002-01-01

    Measurements from the Halogen Occultation Experiment (HALOE) revealed the infrared signature of polar mesospheric clouds (PMCs), for the first time, HALOE PMC observations at eight wavelengths (2.45 - 10 microns) show remarkable agreement with model PMC spectra based on ice particle extinction, and thus provide the first confirmation that water ice is the primary component of PMCs. Because PMCs respond to changes in temperature and water vapor, they are considered an indicator of global climate change. We propose to further the understanding of PMCs using a decade of infrared measurements form HALOE. This effort will characterize PMC spectral properties, extinction profiles, and size distributions. Using this information, HALOE measurements will be used to make simultaneous retrievals of H2O, O3, and temperature, in the presence of PMCs. The simultaneous retrievals of particle properties, H2O, O3, and temperature will be used with HALOE NO data to provide a significant step forward in the knowledge of PMC characteristics and formation conditions. We will challenge fundamental theories of PMC formation, and investigate changes in PMC properties and related conditions over the length of the HALOE measurement record. HALOE has been operating without flaw since it was launched on October 11, 1991. Consequently, ten southern and ten northern PMC seasons have been observed thus far, providing a wealth of data for the study of PMCs and related parameters.

  19. Characterization of Polar Mesospheric Clouds Using Infrared Measurements from HALOE

    NASA Technical Reports Server (NTRS)

    Hervig, Mark E.

    2002-01-01

    Measurements from the Halogen Occultation Experiment (HALOE) revealed the infrared signature of polar mesospheric clouds (PMCs), for the first time, HALOE PMC observations at eight wavelengths (2.45 - 10 microns) show remarkable agreement with model PMC spectra based on ice particle extinction, and thus provide the first confirmation that water ice is the primary component of PMCs. Because PMCs respond to changes in temperature and water vapor, they are considered an indicator of global climate change. We propose to further the understanding of PMCs using a decade of infrared measurements form HALOE. This effort will characterize PMC spectral properties, extinction profiles, and size distributions. Using this information, HALOE measurements will be used to make simultaneous retrievals of H2O3, and temperature, in the presence of PMCs. The simultaneous retrievals of particle properties, H2O3, and temperature will be used with HALOE NO data to provide a significant step forward in the knowledge of PMC characteristics and formation conditions. We will challenge fundamental theories of PMC formation, and investigate changes in PMC properties and related conditions over the length of the HALOE measurement record. HALOE has been operating without flaw since it was launched on October 11, 1991. Consequently, ten southern and ten northern PMC seasons have been observed thus far, providing a wealth of data for the study of PMC and related parameters.

  20. LSE-Sign: A lexical database for Spanish Sign Language.

    PubMed

    Gutierrez-Sigut, Eva; Costello, Brendan; Baus, Cristina; Carreiras, Manuel

    2016-03-01

    The LSE-Sign database is a free online tool for selecting Spanish Sign Language stimulus materials to be used in experiments. It contains 2,400 individual signs taken from a recent standardized LSE dictionary, and a further 2,700 related nonsigns. Each entry is coded for a wide range of grammatical, phonological, and articulatory information, including handshape, location, movement, and non-manual elements. The database is accessible via a graphically based search facility which is highly flexible both in terms of the search options available and the way the results are displayed. LSE-Sign is available at the following website: http://www.bcbl.eu/databases/lse/.