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Sample records for acute tarsal tunnel

  1. Tenosynovial osteochondromatosis of the tarsal tunnel

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    Sugimoto, Kazuya; Iwai, Makoto [Department of Orthopaedic Surgery, Saiseikai Nara Hospital, 4-643 Hachijo, Nara-shi, Nara (Japan); Kawate, Kenji; Yajima, Hiroshi; Takakura, Yoshinori [Department of Orthopaedic Surgery, Nara Medical University, 840 Shijo-cho, Kashihara-shi, Nara (Japan)

    2003-02-01

    A case of tenosynovial osteochondromatosis in the tarsal tunnel in a 23-year-old man is presented. The lesion was treated surgically, and multiple osteochondromas were excised, which had no continuity with any tarsal bone or joint cavity but did with the sheaths of the flexor digitorum longus and flexor hallucis longus. Histologic examination of the lesion showed a fibrous capsule, hyaline cartilage and extensive areas of cancellous bone. Necrosis and mitosis were absent in the hyaline cartilage and there were no synovial nodules indicative of synovial metaplasia. The macroscopic findings showed ''end-stage'' tenosynovial osteochondromatosis. There was no evidence of recurrence 5 years after operation, and the patient remains free of symptoms. (orig.)

  2. The tarsal tunnel syndrome in children.

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    Albrektsson, B; Rydholm, A; Rydholm, U

    1982-01-01

    There are few reports on the tarsal tunnel syndrome in children. This paper concerns 10 such children. In adults the syndrome is equally distributed among the sexes but all these children were girls. Trauma preceded the symptoms in only two cases. The symptoms differed in some aspects from those usually seen in adults. Six of the children walked with the affected foot in supination. Three of the six, and one other, used crutches at intervals. All were operated on and at follow-up nine were symptom-free and the tenth had improved.

  3. Tarsal tunnel disease and talocalcaneal coalition: MRI features

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    FitzGerald Alaia, Erin; Rosenberg, Zehava Sadka; Bencardino, Jenny T.; Ciavarra, Gina A.; Petchprapa, Catherine N. [New York University Langone Medical Center, New York, NY (United States); Rossi, Ignacio [New York University Langone Medical Center, New York, NY (United States); Centro de Diagnostico Dr. Enrique Rossi, Buenos Aires (Argentina)

    2016-11-15

    To assess, utilizing MRI, tarsal tunnel disease in patients with talocalcaneal coalitions. To the best of our knowledge, this has only anecdotally been described before. Sixty-seven ankle MRIs with talocalcaneal coalition were retrospectively reviewed for disease of tendons and nerves of the tarsal tunnel. Interobserver variability in diagnosing tendon disease was performed in 30 of the 67 cases. Tarsal tunnel nerves were also evaluated in a control group of 20 consecutive ankle MRIs. Entrapment of the flexor hallucis longus tendon (FHL) by osseous excrescences was seen in 14 of 67 cases (21 %). Attenuation, split tearing, tenosynovitis, or tendinosis of the FHL was present in 26 cases (39 %). Attenuation or tenosynovitis was seen in the flexor digitorum longus tendon (FDL) in 18 cases (27 %). Tenosynovitis or split tearing of the posterior tibial tendon (PT) was present in nine cases (13 %). Interobserver variability ranged from 100 % to slight depending on the tendon and type of disease. Intense increased signal and caliber of the medial plantar nerve (MPN), indicative of neuritis, was seen in 6 of the 67 cases (9 %). Mildly increased T2 signal of the MPN was seen in 15 (22 %) and in 14 (70 %) of the control group. Talocalcaneal coalitions may be associated with tarsal tunnel soft tissue abnormalities affecting, in decreasing order, the FHL, FDL, and PT tendons, as well as the MPN. This information should be provided to the referring physician in order to guide treatment and improve post-surgical outcome. (orig.)

  4. Tarsal tunnel disease and talocalcaneal coalition: MRI features

    International Nuclear Information System (INIS)

    FitzGerald Alaia, Erin; Rosenberg, Zehava Sadka; Bencardino, Jenny T.; Ciavarra, Gina A.; Petchprapa, Catherine N.; Rossi, Ignacio

    2016-01-01

    To assess, utilizing MRI, tarsal tunnel disease in patients with talocalcaneal coalitions. To the best of our knowledge, this has only anecdotally been described before. Sixty-seven ankle MRIs with talocalcaneal coalition were retrospectively reviewed for disease of tendons and nerves of the tarsal tunnel. Interobserver variability in diagnosing tendon disease was performed in 30 of the 67 cases. Tarsal tunnel nerves were also evaluated in a control group of 20 consecutive ankle MRIs. Entrapment of the flexor hallucis longus tendon (FHL) by osseous excrescences was seen in 14 of 67 cases (21 %). Attenuation, split tearing, tenosynovitis, or tendinosis of the FHL was present in 26 cases (39 %). Attenuation or tenosynovitis was seen in the flexor digitorum longus tendon (FDL) in 18 cases (27 %). Tenosynovitis or split tearing of the posterior tibial tendon (PT) was present in nine cases (13 %). Interobserver variability ranged from 100 % to slight depending on the tendon and type of disease. Intense increased signal and caliber of the medial plantar nerve (MPN), indicative of neuritis, was seen in 6 of the 67 cases (9 %). Mildly increased T2 signal of the MPN was seen in 15 (22 %) and in 14 (70 %) of the control group. Talocalcaneal coalitions may be associated with tarsal tunnel soft tissue abnormalities affecting, in decreasing order, the FHL, FDL, and PT tendons, as well as the MPN. This information should be provided to the referring physician in order to guide treatment and improve post-surgical outcome. (orig.)

  5. The value of MRI iniIdiopathic tarsal tunnel syndrome by measuring the cross-sectional area of tarsal tunnel

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    Kim, Min Jung; Jeong, Yu Mi; Lee, Sheen Woo; Choi Seung; Kim, Jeong Ho; Park, Hong Gi [Gachon University, Gil Hospital, Incheon (Korea, Republic of)

    2015-03-15

    The purpose of this study was to evaluate the use of MRI as a diagnostic test in tarsal tunnel syndrome. There are no published reports with this aim and no diagnostic standard for idiopathic tarsal tunnel syndrome (TTS) using imaging modalities. We retrospectively searched our Picture Archiving and Communication System data and medical records to identify patients who were clinically and electomyographically diagnosed with idiopathic TTS without space-occupying lesion on MRI. Twenty five patients were included in the patient group. Another twenty-five patients who underwent ankle MRI for Achilles tendon disease were selected and included in the control group. Cross-sectional areas (CSA) of tarsal tunnel were manually measured independently by two radiologists who were blinded to clinical and surgical results, using three-dimensional reconstruction software in our hospital. Measurements were done on axial images at three levels (level 1, tibiotalar joint level; level 2, medial malleolar tip level; level 3, sustentaculum tali level). Patient and control group data were statistically analyzed by the Mann-Whitney test. The mean values of CSA at levels 1, 2, and 3 of the tarsal tunnel were 87.8 mm2, 98.2 mm2, and 105.2 mm2, respectively in the patient group; and 100.0 mm2, 113.8 mm2, and 127.9 mm2 in the control group, respectively, in reader 1; and 86.2 mm2, 97.6 mm2, 105.2 mm2, respectively in the patient group; and 99.7 mm2, 112.3 mm2, 124.4 mm2, respectively, in the control group, in reader 2. The mean CSA in the patient group was significantly less than that of the control group at all three levels (p < 0.05). Intra-class correlation coefficient value between reader 1 and reader 2 were 0.98 in group 1, and 0.97 in group 2, respectively. MRI can be helpful in the assessment of idiopathic tarsal tunnel syndrome. CSA measurements of tarsal tunnel at each level may predict TTS even though there are no space occupying lesions in the tarsal tunnel on MRI.

  6. The Usefulness of the Preoperative Magnetic Resonance Imaging Findings in the Evaluation of Tarsal Tunnel Syndrome

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    Jung, Hyun Jin; Lee, Sheen Woo; Jeong, Yu Mi; Choi, Hye Young; Kim, Hyung Sik [Dept. of Radiology, Gil Hospital, Gacheon University College of Medicine, Incheon (Korea, Republic of); Park, Hong Gi; Kwak, Ji Hoon [Dept. of Orthopedic Surgery, Gil Hospital, Gacheon University College of Medicine, Incheon (Korea, Republic of)

    2012-02-15

    The purpose of this study was to access the diverse conditions that lead to the clinical manifestations of tarsal tunnel syndrome and evaluate the usefulness of magnetic resonance imaging (MRI) in preoperative evaluation. Thirty-three patients who underwent ankle MRI and surgery under the impression of tarsal tunnel syndrome were retrospectively analyzed. The findings on ankle MRI were categorized into space occupying lesions within the tarsal tunnel, space occupying lesions of the tunnel wall, and non-space occupying lesions. Associated plantar muscle atrophy was also evaluated. Medical records were reviewed for correlation of nerve conduction velocity (NCV) and surgical findings. There were 21 space occupying lesions of the tarsal tunnel, and eight lesions of tarsal tunnel wall. There were three cases with accessory muscle, three with tarsal coalition, five with ganglion cysts, one neurogenic tumor, five flexor retinaculum hypertrophy, three varicose veins, and nine with tenosynovitis of the posterior tibialis, flexor digitorum longus, or flexor hallucis longus tendon. One patient was found to have a deltoid ligament sprain. Of the 32, eight patients experienced fatty atrophic change within any one of the foot muscles. NCV was positive in 79% of the MRI-positive lesions. MRI provides detailed information on ankle anatomy, which includes that of tarsal tunnel and beyond. Pathologic conditions that cause or mimic tarsal tunnel syndrome are well demonstrated. MRI can enhance surgical planning by indicating the extent of decompression required, and help with further patient management. Patients with tarsal tunnel syndrome can greatly benefit from preoperative MRI. However, it should be noted that not all cases with tarsal tunnel syndrome have MRI-demonstrable causes.

  7. The Usefulness of the Preoperative Magnetic Resonance Imaging Findings in the Evaluation of Tarsal Tunnel Syndrome

    International Nuclear Information System (INIS)

    Jung, Hyun Jin; Lee, Sheen Woo; Jeong, Yu Mi; Choi, Hye Young; Kim, Hyung Sik; Park, Hong Gi; Kwak, Ji Hoon

    2012-01-01

    The purpose of this study was to access the diverse conditions that lead to the clinical manifestations of tarsal tunnel syndrome and evaluate the usefulness of magnetic resonance imaging (MRI) in preoperative evaluation. Thirty-three patients who underwent ankle MRI and surgery under the impression of tarsal tunnel syndrome were retrospectively analyzed. The findings on ankle MRI were categorized into space occupying lesions within the tarsal tunnel, space occupying lesions of the tunnel wall, and non-space occupying lesions. Associated plantar muscle atrophy was also evaluated. Medical records were reviewed for correlation of nerve conduction velocity (NCV) and surgical findings. There were 21 space occupying lesions of the tarsal tunnel, and eight lesions of tarsal tunnel wall. There were three cases with accessory muscle, three with tarsal coalition, five with ganglion cysts, one neurogenic tumor, five flexor retinaculum hypertrophy, three varicose veins, and nine with tenosynovitis of the posterior tibialis, flexor digitorum longus, or flexor hallucis longus tendon. One patient was found to have a deltoid ligament sprain. Of the 32, eight patients experienced fatty atrophic change within any one of the foot muscles. NCV was positive in 79% of the MRI-positive lesions. MRI provides detailed information on ankle anatomy, which includes that of tarsal tunnel and beyond. Pathologic conditions that cause or mimic tarsal tunnel syndrome are well demonstrated. MRI can enhance surgical planning by indicating the extent of decompression required, and help with further patient management. Patients with tarsal tunnel syndrome can greatly benefit from preoperative MRI. However, it should be noted that not all cases with tarsal tunnel syndrome have MRI-demonstrable causes.

  8. Case Study of Oriental Medicine Treatment with acupotomy Therpy of the Tarsal tunnel Syndrome

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    Lim Na-ra

    2009-03-01

    Full Text Available Purpose : In order to estimate clinical effects of Oriental Medicine Treatment with acupotomy therapy of Tarsal tunnel Syndrome Methods : From 5th November, 2008 to 8th November, 2008, 1 male patient diagnosed as Tarsal tunnel syndrome(clinical diagnosed was treated with general oriental medicine therapy (acupuncture, moxibustion, cupping, physical therapy, herbal medication and acupotomy. Results : The patient's Rt foot paresthesia, pain were remarkably improved. Conclusions : This study demonstrates that oriental medical treatment with acuputomy therapy has notable effect in improving symptoms of tarsal tunnel syndrome. as though we had not wide experience in this treatment, more research is needed.

  9. Bilateral posterior tarsal tunnel syndrome caused by accessory flexor digitorum longus; case report and surgical technique.

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    Schmidt-Hebbel, A; Elgueta, J; Villa, A; Mery, P; Filippi, J

    To present a case report of bilateral posterior tarsal tunnel syndrome (PTTS) caused by an accessory flexor digitorum longus (AFDL), including the surgical technique and a review of the literature. Twenty-nine year old male diagnosed with bilateral PTTS, refractory to conservative management, with 53 points on the preoperative AOFAS score. MR of both ankles showed an AFDL within the tarsal tunnel, in close relationship to the posterior tibial nerve. Bilateral tarsal tunnel decompression and AFDL resection was performed. There were no post-operative complications. At 6 months after surgery, the patient had no pain and had 87 points on the AOFAS score. The PTTS is an entrapment neuropathy of the posterior tibial nerve or one of its terminal branches. A rare cause is the presence of an AFDL, and its resection is associated with good clinical results. Careful scar tissue resection and neurolysis is recommended. Knowing the normal pathway and anatomical variability of the posterior tibial nerve and its branches is essential to avoid iatrogenic injury. In our case report, MR and intraoperative findings identified a bilateral FDLA in close relationship to the common flexor digitorum, an unusual finding, with few reports in current literature. Careful tarsal tunnel decompression and AFDL resection in our patient with bilateral symptomatic PTTS has good clinical results and no complications, particularly when diagnosed and treated early. Copyright © 2015 SECOT. Publicado por Elsevier España, S.L.U. All rights reserved.

  10. Bilateral anterior tarsal tunnel syndrome variant secondary to extensor hallucis brevis muscle hypertrophy in a ballet dancer: a case report.

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    Tennant, Joshua N; Rungprai, Chamnanni; Phisitkul, Phinit

    2014-12-01

    We present a case of bilateral anterior tarsal tunnel syndrome secondary EHB hypertrophy in a dancer, with successful treatment with bilateral EHB muscle excisions for decompression. The bilateral presentation of this case with the treatment of EHB muscle excision is the first of its type reported in the literature. Copyright © 2014 European Foot and Ankle Society. Published by Elsevier Ltd. All rights reserved.

  11. The Impact of Tarsal Tunnel Syndrome on Cold Sensation in the Pedal Extremities.

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    Kokubo, Rinko; Kim, Kyongsong; Isu, Toyohiko; Morimoto, Daijiro; Iwamoto, Naotaka; Kobayashi, Shiro; Morita, Akio

    2016-08-01

    Tarsal tunnel syndrome (TTS) is an entrapment neuropathy of the posterior tibial nerve in the tarsal tunnel. It is not known whether vascular or neuropathic factors are implicated in the cause of a cold sensation experienced by patients. Therefore, we studied the cold sensation in the pedal extremities of patients who did or did not undergo TTS surgery. Our study population comprised 20 patients with TTS (38 feet); 1 foot was affected in 2 patients and both feet in 18 patients. We acquired the toe-brachial pressure index to evaluate perfusion of the sole and toe perfusion under 4 conditions: the at-rest position (condition 1); the at-rest position with compression of the foot dorsal artery (condition 2); the Kinoshita foot position (condition 3); and the Kinoshita foot position with foot dorsal artery compression (condition 4). Patients who reported abatement in the cold sensation during surgery underwent intraoperative reocclusion of the tibial artery to check for the return of the cold sensation. The toe-brachial pressure index for conditions 1 and 3 averaged 0.82 ± 0.09 and 0.81 ± 0.11, respectively; for conditions 2 and 4, it averaged 0.70 ± 0.11 and 0.71 ± 0.09, respectively. Among the 16 operated patients, the cold sensation in 7 feet improved intraoperatively; transient reocclusion of the tibial artery did not result in the reappearance of the cold sensation. Our findings suggest that the cold sensation in the feet of our patients with TTS was associated with neuropathic rather than vascular factors. Copyright © 2016 Elsevier Inc. All rights reserved.

  12. Evaluation of peripheral microcirculation improvement of foot after tarsal tunnel release in diabetic patients by transcutaneous oximetry.

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    Trignano, Emilio; Fallico, Nefer; Chen, Hung-Chi; Faenza, Mario; Bolognini, Alfonso; Armenti, Andrea; Santanelli Di Pompeo, Fabio; Rubino, Corrado; Campus, Gian Vittorio

    2016-01-01

    According to recent studies, peripheral nerve decompression in diabetic patients seems to not only improve nerve function, but also to increase microcirculation; thus decreasing the incidence of diabetic foot wounds and amputations. However, while the postoperative improvement of nerve function is demonstrated, the changes in peripheral microcirculation have not been demonstrated yet. The aim of this study is to assess the degree of microcirculation improvement of foot after the tarsal tunnel release in the diabetic patients by using transcutaneous oximetry. Twenty diabetic male patients aged between 43 and 72 years old (mean age 61.2 years old) suffering from diabetic peripheral neuropathy with superimposed nerve compression underwent transcutaneous oximetry (PtcO2) before and after tarsal tunnel release by placing an electrode on the skin at the level of the dorsum of the foot. Eight lower extremities presented diabetic foot wound preoperatively. Thirty-six lower extremities underwent surgical release of the tibialis posterior nerve only, whereas four lower extremities underwent the combined release of common peroneal nerve, anterior tibialis nerve, and posterior tibialis nerve. Preoperative values of transcutaneous oximetry were below the critical threshold, that is, lower than 40 mmHg (29.1 ± 5.4 mmHg). PtcO2 values at one month after surgery (45.8 ± 6.4 mmHg) were significantly higher than the preoperative ones (P = 0.01). The results of postoperative increase in PtcO2 values demonstrate that the release of the tarsal tunnel determines a relevant increase in microcirculation in the feet of diabetic patients. © 2015 Wiley Periodicals, Inc.

  13. Value of computed tomography arthrography with delayed acquisitions in the work-up of ganglion cysts of the tarsal tunnel: report of three cases

    International Nuclear Information System (INIS)

    Omoumi, Patrick; Gheldere, Antoine de; Leemrijse, Thibaut; Galant, Christine; Van den Bergh, Peter; Malghem, Jacques; Simoni, Paolo; Berg, Bruno C.V.; Lecouvet, Frederic E.

    2010-01-01

    Ganglion cysts are a common cause of tarsal tunnel syndrome. As in other locations, these cysts are believed to communicate with neighboring joints. The positive diagnosis and preoperative work-up of these cysts require identification and location of the cyst pedicles so that they may be excised and the risk of recurrence decreased. This can be challenging with ultrasonography and magnetic resonance (MR) imaging. We present three cases of symptomatic ganglion cysts of the tarsal tunnel, diagnosed by MR imaging, where computed tomography (CT) arthrography with delayed acquisitions helped to confirm the diagnosis and identify precisely the topography of the communication with the subtalar joint. These cases provide new evidence of the articular origin of ganglion cysts developing in the tarsal tunnel. (orig.)

  14. [Assessing the treatment for sacroiliac joint dysfunction, piriformis syndrome and tarsal tunnel syndrome associated with lumbar degenerative disease].

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    Morimoto, Daijiro; Isu, Toyohiko; Shimoda, Yuusuke; Hamauchi, Shuuji; Sasamori, Tooru; Sugawara, Atsushi; Kim, Kyongsong; Matsumoto, Ryouji; Isobe, Masanori

    2009-09-01

    Sacroiliac joint (SIJ) dysfunction, piriformis syndrome (PFS) and tarsal tunnel syndrome (TTS) produce symptoms similar to lumbar degenerative disease (LDD). Patients who have these diseases plus LDD sometimes experience residual symptoms after surgery for LDD. We therefore assessed the results of treatment of SIJ dysfunction, PFS and TTS associated with LDD. We assessed 25 patients who underwent surgery for LDD and were affected with SIJ dysfunction (12 patients), PFS (7 patients) or TTS (6 patients). SIJ dysfunction was treated with rest, drugs, pelvic band and sacroiliac joint block. PFS was treated with rest, drugs, physical exercise, injection of local anesthetic into the piriformis muscle, and surgical resection of the piriformis muscle. TTS was treated with drugs and tarsal tunnel opening. We analyzed the improvement score and recovery rate (JOA score) for both LDD surgery and the treatment of SIJ dysfunction, PFS and TTS. Symptom improvement was observed in all patients with SIJ dysfunction and PFS and in 4 patients with TTS. The improvement score and recovery rate of treatments for SIJ dysfunction, PFS and TTS were lower than those of surgery for LDD. The improvement score and recovery rate of treatment for SIJ dysfunction, PFS and TTS were not as high as those for LDD. To enhance patient satisfaction, it is important to consider these complicating diseases when designing treatments for LDD.

  15. Tarsal Tunnel Syndrome

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    ... and maintains the structures contained within the tunnel—arteries, veins, tendons and nerves. One of these structures ... Terms and Conditions | Site Map 8725 West Higgins Road, Suite 555, Chicago, IL 60631-2724 Phone: (773) ...

  16. FRACTURE OF THE CENTRAL TARSAL BONE IN NONRACEHORSES: FOUR CASES.

    Science.gov (United States)

    Knuchell, Jeannie A; Spriet, Mathieu; Galuppo, Larry D; Katzman, Scott A

    2016-07-01

    Fractures of the central tarsal bone are a rarely recognized cause of acute severe hind limb lameness in nonracehorses. Diagnosis of these fractures can be challenging and little is known about their configuration or outcome. The objectives of this retrospective case series study were to describe the clinical features, imaging findings, and outcomes of fractures of the central tarsal bone in a sample of nonracehorses. Medical records from 2001 to 2014 were searched for cases of central tarsal bone fractures in nonracehorses. All available imaging findings including radiography, ultrasound, computed tomography (CT), and/or nuclear scintigraphy were reviewed. History, clinical presentation, and outcome were collected from the records. Four horses met the inclusion criteria. All had a similar configuration as a simple nondisplaced slab fracture in a dorsomedial to plantarolateral orientation. Initial radiographs failed to reveal the fracture in three of four cases. When additional plantarolateral-dorsomedial oblique radiographic views were obtained, the fracture could be identified in all cases. Fractures of the central tarsal bone seemed to occur in a consistent dorsomedial to plantarolateral orientation in this sample of nonracehorses, which is different from the configuration previously reported in racehorses. While CT can be used for detection and assessment of these fractures, authors propose that radiography can also identify these fractures with the appropriate view. Authors recommend the use of several plantarolateral to dorsomedial radiographic projections at varying degrees of obliquity for horses with a suspected central tarsal bone fracture. © 2016 American College of Veterinary Radiology.

  17. Tarsal bone disintegration in leprosy

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    Haverson, G.; Warren, A.G.

    1979-01-01

    Tarsal bone disintegration is characterised by fragmentation and progressive collapse of one or more tarsal bones. It occurs in 10% of leprosy patients, and is responsible for many severe foot deformities associated with this disease. The main cause is micro-traumata, but sensory impairment, sepsis and osteoporosis are predisposing factors. In this series of 400 consecutive patients the talus and navicular were involved most frequently (72% of 119 tarsal lesions). Treatment, including prolonged immobilisation of the foot, results in dense sclerosis of the affected bone, and leaves a functional limb. Initial radiological features include bone fragmentation, calcified fragments in adjacent soft tissues, linear fractures, progressive compression and deformity of the affected bone, loss of density of the affected bone and flattening of the longitudinal plantar arch. Illustrative case histories are presented, and the differential diagnosis discussed. (author)

  18. Acute carpal tunnel syndrome in a patient with haemophilia.

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    Mayne, Alistair Ivan William; Howard, Anthony; Kent, Matthew; Banks, Joanne

    2012-07-03

    Acute carpal tunnel syndrome (CTS) is a rare surgical condition usually resulting from wrist trauma. We present the case of a young haemophilic man who developed acute CTS following trivial injury. The patient was initially managed conservatively but symptom progression resulted in carpal tunnel decompression. A literature review and management approach are presented. This is an important complication of haemophilia to be aware of as prompt conservative management can obviate the need for surgery. This case is useful in (a) highlighting the importance of considering a patient's medical history when formulating differential diagnoses and (b) outlining a management approach to this condition.

  19. Bone scintigraphy as an aid in the diagnosis of occult distal tarsal bone trauma in three horses

    International Nuclear Information System (INIS)

    Stover, S.M.; Hornof, W.J.; Richardson, G.L.; Meagher, D.M.

    1986-01-01

    History, physical examination, and bone scintigraphy were used to diagnose central and/or third tarsal bone trauma in 3 acutely lame horses. In all 3 cases, the results of initial radiographic examination were negative. Bone scintigraphy revealed focal, intense radioisotope uptake at the level of the distal tarsal bones in the 3 horses. Radiographs obtained 4 weeks after injury in one horse demonstrated a slab fracture of the central tarsal bone. Conservative management of the tarsal bone disease resulted in acceptable return to function in all 3 horses

  20. Conservative treatment of patients with tarsal coalitions

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    A. V. Sapogoosky

    2015-01-01

    Full Text Available Tarsal coalition is a pathological condition with abnormal fusion between two or more tarsal bones. The aim of the study was to evaluate effectiveness of conservative treatment in patients with tarsal coalitions. The treatment included reducing the intensity of physical activity, medication, orthotics, physiotherapy. For evaluation of effectiveness of the treatment, we used the AOFAS scale. The results of the study demonstrated that conservative treatment in patients with tarsal coalitions was focused onon temporary pain release. Conservative treatment has limited efficacy for patients with symptomatic tarsal coalitions because of short pain release in the majority of children (98 %. The indications for conservative treatment in patients with symptomatic tarsal coalitions should be pain and hindfoot valgus less than 15°. In other cases, conservative treatment should be considered as preoperative preparation.

  1. Rhinosporidiosis of the tarsal conjunctiva

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    Akshay Gopinathan Nair

    2015-01-01

    Full Text Available Rhinosporidiosis is a rare infection caused by Rhinosporidium seeberi, an organism classified in its own class, mesomycetozoea. It commonly affects mucus membranes namely the nasal mucosa, pharynx and the conjunctiva. We present the case of an 8-year-old female who presented with a flat, red, vascular, fleshy, pedunculated mass arising from the tarsal conjunctiva of the right upper eyelid. The mass was completely excised. On histopathological examination, multiple sporangia were seen in various stages of degeneration, consistent with rhinosporidiosis. The diagnosis of rhinosporidiosis is based solely on its microscopic features, and the treatment is surgical excision. This condition is endemic in the temperate regions of the Indian subcontinent, but it has been known to occur even in the colder regions of North America and Eastern Europe. Although a rare clinical entity, the possibility of rhinosporidiosis must be borne in mind when evaluating any polypoidal conjunctival mass.

  2. Ewing's sarcoma of the tarsal bone

    International Nuclear Information System (INIS)

    Kwon, Jung Hyeok; Kim, Yong Sun; Kim, Tae Hun; Park, In Kyu; Kim, Yong Joo; Kang, Duk Sik; Sohn, Kyung Rak

    1985-01-01

    The Ewing's sarcoma comprises approximately less than 10 percent of malignant bone tumors and 5 percent of all bone tumors, occurs in almost all bones of the body, and presents a widely divergent roentgenographic manifestations. The tarsal bones are involved only 2 percent in the Ewing's sarcoma. Two cases experienced by authors and ten cases published in literatures of Ewing's sarcoma of the tarsal bone were analyzed retrospectively. The result were as follows: 1. Of the tarsal bones, the calcaneus was 7 cases, the talus 4 cases, cuneiform 1 case. 2. Female was affected more commonly than male, the ratio being 4 to 1 in the tarsal bones. 3. About sixty percent of total cases in the tarsal bones had evidence of diffuse sclerotic pattern. All the cases of the talus had evidence of diffuse sclerotic pattern. 4. The diseases to be considered in differential diagnosis are as follows: avascular necrosis, tuberculous osteomyelitis, osteosarcoma, and pyogenic osteomyelitis. 5. The diffuse sclerosis radiographically showed a close relation with dead bone resulting from avascular necrosis due to tumor infiltration histologically. Periosteal reactive new bone and osteoid deposition on the dead bone were also correlated with diffuse sclerosis. 6. Because it is difficult to differentiate sclerotic lesions in the tarsal bones by radiographic methods alone, all such lesions should be subject to biopsy as early as possible

  3. Ewing's sarcoma of the tarsal bone

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    Kwon, Jung Hyeok; Kim, Yong Sun; Kim, Tae Hun; Park, In Kyu; Kim, Yong Joo; Kang, Duk Sik; Sohn, Kyung Rak [College of Medicine, Kyungpook National University, Daegu (Korea, Republic of)

    1985-06-15

    The Ewing's sarcoma comprises approximately less than 10 percent of malignant bone tumors and 5 percent of all bone tumors, occurs in almost all bones of the body, and presents a widely divergent roentgenographic manifestations. The tarsal bones are involved only 2 percent in the Ewing's sarcoma. Two cases experienced by authors and ten cases published in literatures of Ewing's sarcoma of the tarsal bone were analyzed retrospectively. The result were as follows: 1. Of the tarsal bones, the calcaneus was 7 cases, the talus 4 cases, cuneiform 1 case. 2. Female was affected more commonly than male, the ratio being 4 to 1 in the tarsal bones. 3. About sixty percent of total cases in the tarsal bones had evidence of diffuse sclerotic pattern. All the cases of the talus had evidence of diffuse sclerotic pattern. 4. The diseases to be considered in differential diagnosis are as follows: avascular necrosis, tuberculous osteomyelitis, osteosarcoma, and pyogenic osteomyelitis. 5. The diffuse sclerosis radiographically showed a close relation with dead bone resulting from avascular necrosis due to tumor infiltration histologically. Periosteal reactive new bone and osteoid deposition on the dead bone were also correlated with diffuse sclerosis. 6. Because it is difficult to differentiate sclerotic lesions in the tarsal bones by radiographic methods alone, all such lesions should be subject to biopsy as early as possible.

  4. The adult tarsal navicular: why it matters

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    Scott-Moncrieff, A. [Univ. of British Columbia, Vancouver, British Columbia (Canada)], E-mail: ascottmo@interchange.ubc.ca; Forster, B.B.; Andrews, G. [Dept. of Radiology, Univ. of British Columbia Hospital, Vancouver, British Columbia (Canada); Khan, K. [Dept. of Family Practice, Univ. of British Columbia Hospital, Vancouver, British Columbia (Canada); Allan McGavin Sports Medicine Clinic, Vancouver, British Columbia (Canada)

    2007-12-15

    The adult tarsal navicular is an integral part of the midfoot. Many unique pathological conditions affect its function, and while subtle in their presentation, they can be significant sources of pain and deformity. Recognition of these abnormalities in imaging is essential to obtaining prompt diagnoses and instigating early management interventions. In this pictorial essay, accessory ossicles, stress fractures, avascular necrosis, and tarsal coalitions involving the navicular will be discussed in terms of their characteristic imaging findings. Normal anatomy and biomechanical functional aspects of the navicular will be reviewed and multiple images from plain film, ultrasound, bone scan, computed tomography, and magnetic resonance imaging will be presented. Improved familiarity with the adult tarsal navicular and its various abnormalities will enable radiologists to recognize its importance in the differential diagnosis of midfoot pathology. (author)

  5. The adult tarsal navicular: why it matters

    International Nuclear Information System (INIS)

    Scott-Moncrieff, A.; Forster, B.B.; Andrews, G.; Khan, K.

    2007-01-01

    The adult tarsal navicular is an integral part of the midfoot. Many unique pathological conditions affect its function, and while subtle in their presentation, they can be significant sources of pain and deformity. Recognition of these abnormalities in imaging is essential to obtaining prompt diagnoses and instigating early management interventions. In this pictorial essay, accessory ossicles, stress fractures, avascular necrosis, and tarsal coalitions involving the navicular will be discussed in terms of their characteristic imaging findings. Normal anatomy and biomechanical functional aspects of the navicular will be reviewed and multiple images from plain film, ultrasound, bone scan, computed tomography, and magnetic resonance imaging will be presented. Improved familiarity with the adult tarsal navicular and its various abnormalities will enable radiologists to recognize its importance in the differential diagnosis of midfoot pathology. (author)

  6. Peculiar chondroblastoma involving multiple tarsal bones

    International Nuclear Information System (INIS)

    Fukunaga, Masaharu; Asanuma, Kazuo; Irie, Takeo

    2010-01-01

    A case of peculiar chondroblastoma involving multiple tarsal bones in a 49-year-old woman is described. The patient presented with pain and swelling of the right foot. Radiographs revealed a lytic expansile lesion of medial, intermediate, and lateral cuneiform bones, navicular, cuboid, and tarsal bones of the right foot, indicating a malignant tumor. Biopsies demonstrated a diffuse proliferation of round cells with eccentric and indented nuclei with longitudinal grooves and eosinophilic cytoplasm. Atypia was prominent, but mitotic figures were rare. The stroma was chondroid with focal chicken-wire calcification. On electron microscopy, the tumor exhibited chondroblastic features. The patient is alive with the tumor 7 years after radiotherapy. The tumor is considered a chondroblastoma with low malignant potential. (orig.)

  7. Peculiar chondroblastoma involving multiple tarsal bones

    Energy Technology Data Exchange (ETDEWEB)

    Fukunaga, Masaharu [Jikei University School of Medicine, Department of Pathology, Tokyo (Japan); the Jikei University Daisan Hospital, Department of Pathology, Tokyo (Japan); Asanuma, Kazuo [Jikei University School of Medicine, Department of Orthopedic Surgery, Tokyo (Japan); Irie, Takeo [Jikei University School of Medicine, Department of Radiology, Tokyo (Japan)

    2010-07-15

    A case of peculiar chondroblastoma involving multiple tarsal bones in a 49-year-old woman is described. The patient presented with pain and swelling of the right foot. Radiographs revealed a lytic expansile lesion of medial, intermediate, and lateral cuneiform bones, navicular, cuboid, and tarsal bones of the right foot, indicating a malignant tumor. Biopsies demonstrated a diffuse proliferation of round cells with eccentric and indented nuclei with longitudinal grooves and eosinophilic cytoplasm. Atypia was prominent, but mitotic figures were rare. The stroma was chondroid with focal chicken-wire calcification. On electron microscopy, the tumor exhibited chondroblastic features. The patient is alive with the tumor 7 years after radiotherapy. The tumor is considered a chondroblastoma with low malignant potential. (orig.)

  8. Central tarsal bone fracture in the border collie.

    Science.gov (United States)

    Guilliard, M

    2007-07-01

    Fracture of the plantar process of the central tarsal bone together with a dorsomedial displacement of the body of the bone was seen in six border collies. All injuries occurred during free exercise, with no extrinsic trauma. Three dogs had concomitant tarsal fractures. Primary treatment was by lag screwing the central tarsal bone to the fourth tarsal bone. All cases eventually made an excellent recovery. The superficial radiographic appearance was of a luxation of the bone as reported in a previous series, but appraisal of the radiographs showed evidence of fracture in all cases. A cadaver study to assess the mechanism of luxation showed that it is unlikely to occur naturally.

  9. Placing of tunneled central venous catheters prior to induction chemotherapy in children with acute lymphoblastic leukemia

    DEFF Research Database (Denmark)

    Handrup, Mette Møller; Møller, Jens Kjølseth; Frydenberg, Morten

    2010-01-01

    BACKGROUND: Tunneled central venous catheters (CVCs) are inevitable in children with acute lymphoid leukemia (ALL). The aim of this study was to evaluate the risk of CVC-related complications in children with ALL in relation to timing of catheter placement and type of catheter. PROCEDURE: All...

  10. The bone scan in tarsal coalition: a case report

    International Nuclear Information System (INIS)

    De Lima, R.T.; Mishkin, F.S.

    1996-01-01

    Tarsal coalition is abnormal fusion of two or more tarsal bones. The union may be fibrous, cartilaginous, or osseous and can be congenital or acquired in response to infection, articular disorders, trauma, or surgery. We report a case of fibrous talocalcaneal coalition in a 15-year-old boy in whom bone scintigraphy employing pinhole lateral views confirmed the clinical diagnosis when plain radiographs showed minimal changes and computed tomography was equivocal. The diagnosis of symptomatic tarsal coalition is important in that it is a common remediable cause of peroneal spastic flat foot, a frequently encountered condition. Scintigraphy provides important information about the presence and localization of this condition. (orig.). With 3 figs

  11. The bone scan in tarsal coalition: a case report

    Energy Technology Data Exchange (ETDEWEB)

    De Lima, R.T. [Department of Radiology, Division of Nuclear Medicine, Harbor-UCLA Medical Center, Torrance, CA (United States); Mishkin, F.S. [Department of Radiology, Division of Nuclear Medicine, Harbor-UCLA Medical Center, Torrance, CA (United States)

    1996-10-01

    Tarsal coalition is abnormal fusion of two or more tarsal bones. The union may be fibrous, cartilaginous, or osseous and can be congenital or acquired in response to infection, articular disorders, trauma, or surgery. We report a case of fibrous talocalcaneal coalition in a 15-year-old boy in whom bone scintigraphy employing pinhole lateral views confirmed the clinical diagnosis when plain radiographs showed minimal changes and computed tomography was equivocal. The diagnosis of symptomatic tarsal coalition is important in that it is a common remediable cause of peroneal spastic flat foot, a frequently encountered condition. Scintigraphy provides important information about the presence and localization of this condition. (orig.). With 3 figs.

  12. Tunneling Schmorl's nodes in an elderly woman treated for acute lymphoblastic leukemia

    Energy Technology Data Exchange (ETDEWEB)

    Leone, A. [Dept. of Radiology, Catholic Univ., Rome (Italy); Cerase, A. [Dept. of Radiology, Catholic Univ., Rome (Italy); Unit of Neuroradiology, Policlinico ' ' Le Scotte' ' , Siena (Italy); Equitani, F.; Pagano, L. [Dept. of Hematology, Catholic Univ., Rome (Italy)

    2000-11-01

    We present a 70-year-old woman with pre-B acute lymphoblastic leukemia in whom serial imaging studies showed the development of multiple vertebral collapse, and communicating superior and inferior Schmorl's nodes creating a longitudinal channel (''tunneling'' Schmorl's nodes) through the anterior aspect of T12 to L3 vertebral bodies of her osteoporotic thoracolumbar spine. This was observed after achieving complete remission of the disease and during maintenance therapy. The finding is felt to be secondary to iatrogenic exacerbation of osteoporosis. (orig.)

  13. Tunneling Schmorl's nodes in an elderly woman treated for acute lymphoblastic leukemia

    International Nuclear Information System (INIS)

    Leone, A.; Cerase, A.; Equitani, F.; Pagano, L.

    2000-01-01

    We present a 70-year-old woman with pre-B acute lymphoblastic leukemia in whom serial imaging studies showed the development of multiple vertebral collapse, and communicating superior and inferior Schmorl's nodes creating a longitudinal channel (''tunneling'' Schmorl's nodes) through the anterior aspect of T12 to L3 vertebral bodies of her osteoporotic thoracolumbar spine. This was observed after achieving complete remission of the disease and during maintenance therapy. The finding is felt to be secondary to iatrogenic exacerbation of osteoporosis. (orig.)

  14. Intradermal therapy (mesotherapy) for the treatment of acute pain in carpal tunnel syndrome: a preliminary study.

    Science.gov (United States)

    Conforti, Giorgio; Capone, Loredana; Corra, Stefano

    2014-01-01

    The carpal tunnel syndrome (CTS) is the most common cause of severe hand pain. In this study we treated acute pain in CTS patients by means of local intradermal injections of anti-inflammatory drugs (mesotherapy). In twenty-five patients (forty-five hands), CTS diagnosis was confirmed by clinical and neurophysiological examination prior to mesotherapy. A mixture containing lidocaine 10 mg, ketoprophen lysine-acetylsalycilate 80 mg, xantinol nicotinate 100 mg, cyanocobalamine 1,000 mcg plus injectable water was used. Sites of injection were three parallel lines above the transverse carpal ligament and two v-shaped lines, one at the base of the thenar eminence, and the other at the base of the hypothenar eminence. The day after the treatment, all but four patients reported a significant reduction in pain and paresthesias. After 12 months, 17 patients had a complete pain relief, eight patients reported recurrence of pain and sensory symptoms and four out of them underwent surgical treatment. With the obvious limits of a small-size open-label study, our results suggest that mesotherapy can temporary relieve pain and paresthesias in most CTS patients and in some cases its effect seems to be long-lasting. Further controlled studies are needed to confirm our preliminary findings and to compare mesotherapy to conventional approaches for the treatment of CTS.

  15. Ganglia of the tarsal sinus: MR imaging features and clinical findings

    International Nuclear Information System (INIS)

    Bauer, Jan S.; Müller, Dirk; Sauerschnig, Martin; Imhoff, Andreas B.; Rechl, H.; Rummeny, Ernst J.; Woertler, Klaus

    2011-01-01

    Purpose: To analyze MR imaging and clinical findings associated with ganglia of the tarsal sinus. Materials and methods: In a record search, ganglia of the tarsal sinus were retrospectively identified in 26 patients (mean age 48 ± 16 years), who underwent MR imaging for chronic ankle pain. Images were reviewed by two radiologists in consensus for size and location of ganglia, lesions of ligaments of the ankle and the tarsal sinus, tendon abnormalities, osteoarthritis, osseous erosions and bone marrow abnormalities. Medical records were reviewed for patient history and clinical findings. Results: Ganglia were associated with the interosseus ligament in 81%, the cervical ligament in 31% and the retinacula in 46% of cases. Signal alterations suggesting degeneration were found in 85%, 50% and 63% in case of the interosseus ligament, the cervical ligament and the retinacula, respectively. Scarring of the anterior talofibular ligament and the fibulocalcaneal ligament was found in 68% and 72% of the patients, respectively, while only 27% of the patients recalled ankle sprains. Ganglia at the retinacula were highly associated with synovitis and tendinosis of the posterior tibial tendon (p < 0.05). Conclusion: All patients with ganglia in the tarsal sinus presented with another pathology at the ankle, suggesting that degeneration of the tarsal sinus may be a secondary phenomenon, due to pathologic biomechanics at another site of the hind foot. Thus, in patients with degenerative changes of the tarsal sinus, one should be alerted and search for underlying pathology, which may be injury of the lateral collateral ligaments in up to 70%.

  16. Immunotherapy of elderly acute myeloid leukemia: light at the end of a long tunnel?

    Science.gov (United States)

    Rafelson, William M; Reagan, John L; Fast, Loren D; Lim, Seah H

    2017-11-01

    Although it is possible to induce remission in the majority of the patients with acute myeloid leukemia (AML), many patients still die due to disease relapse. Immunotherapy is an attractive option. It is more specific. The memory T cells induced by immunotherapy may also provide the long-term tumor immunosurveillance to prevent disease relapse. Although immunotherapy of AML started in the early 1970s, its clinical impact has been disappointing. Recent advances in tumor immunology and immunotherapeutic agents have rekindled interest. Here, we provide a review of the history of AML immunotherapy, discuss why AML is well suited for immunotherapeutic approaches and present the biological obstacles that affect the success of immunotherapy. Finally, we put forward a new paradigm of AML immunotherapy that utilizes a combination of immunotherapeutic agents sequentially to enhance the in vivo tumor immunogenicity and effective priming and propagation of tumor-specific cytotoxic T cells.

  17. The dimensions of the tarsal sinus and canal in different foot positions and its clinical implications

    NARCIS (Netherlands)

    Kleipool, R. P.; Blankevoort, L.; Ruijter, J. M.; Kerkhoffs, G. M. M. J.; Oostra, R. J.

    2017-01-01

    This study presents a reference for the dimensions of the tarsal sinus and canal in healthy adults in different foot positions to facilitate understanding of the kinematics of the subtalar joint, the effect of an implant, and other clinical issues. In a 3D CT stress test on 20 subjects, the right

  18. Biomechanical Comparison of External Fixation and Compression Screws for Transverse Tarsal Joint Arthrodesis.

    Science.gov (United States)

    Latt, L Daniel; Glisson, Richard R; Adams, Samuel B; Schuh, Reinhard; Narron, John A; Easley, Mark E

    2015-10-01

    Transverse tarsal joint arthrodesis is commonly performed in the operative treatment of hindfoot arthritis and acquired flatfoot deformity. While fixation is typically achieved using screws, failure to obtain and maintain joint compression sometimes occurs, potentially leading to nonunion. External fixation is an alternate method of achieving arthrodesis site compression and has the advantage of allowing postoperative compression adjustment when necessary. However, its performance relative to standard screw fixation has not been quantified in this application. We hypothesized that external fixation could provide transverse tarsal joint compression exceeding that possible with screw fixation. Transverse tarsal joint fixation was performed sequentially, first with a circular external fixator and then with compression screws, on 9 fresh-frozen cadaveric legs. The external fixator was attached in abutting rings fixed to the tibia and the hindfoot and a third anterior ring parallel to the hindfoot ring using transverse wires and half-pins in the tibial diaphysis, calcaneus, and metatarsals. Screw fixation comprised two 4.3 mm headless compression screws traversing the talonavicular joint and 1 across the calcaneocuboid joint. Compressive forces generated during incremental fixator foot ring displacement to 20 mm and incremental screw tightening were measured using a custom-fabricated instrumented miniature external fixator spanning the transverse tarsal joint. The maximum compressive force generated by the external fixator averaged 186% of that produced by the screws (range, 104%-391%). Fixator compression surpassed that obtainable with screws at 12 mm of ring displacement and decreased when the tibial ring was detached. No correlation was found between bone density and the compressive force achievable by either fusion method. The compression across the transverse tarsal joint that can be obtained with a circular external fixator including a tibial ring exceeds that

  19. [Synostosis and tarsal coalitions in children. A study of 68 cases in 47 patients].

    Science.gov (United States)

    Rouvreau, P; Pouliquen, J C; Langlais, J; Glorion, C; de Cerqueira Daltro, G

    1994-01-01

    The authors report their experience with tarsal coalitions in children. The purpose of this study was to discuss the origins of the of the calcaneum, and to propose a simple therapeutic strategy for diagnosis and treatment. The study included 47 children (68 feet), with one or more idiopathic tarsal coalitions. All patients had physical examinations to record symptoms, morphology of the foot, mobility of the foot, gait analysis, standard radiographs, and in some cases CT scans or MRI. The average age of the patients was 11.5 years old, 7 patients had a positive family history for tarsal coalitions. 66 per cent of the patients had mild tarsal pain or a history of repeated ankle sprains. The conservative treatment concerned 28 feet: 3 casts, 2 injections of corticosteroids into the subtalar joint, insole-shoes in 3 cases, and abstention in 20 cases. The operative treatment (40 feet) consisted of resection of calcaneonavicular coalitions (24 feet) resection of talocalcaneal coalitions (3 feet), mediotarsal and subtalar arthrodesis (8 feet), resection of calcaneonavicular coalition combined with the "Cavalier'' procedure described by Judet (3 feet), calcaneal osteotomy (2 feet). The mean follow-up was 42 months. The morphology of the involved foot was normal in 33 cases, flat foot was seen in 24 cases (4 peroneal spastic flat feet), pes cavus in 3 cases, club foot in 2 cases, pes varus in 4 cases, "Z'' shaped feet in 2 cases. The radiological examination was demonstrative of tarsal coalition in 61 feet. 7 tarsal coalitions were seen during operative procedures. The location or the coalition was calcaneonavicular (57), talocalcaneal (16), talo-navicular (8), calcaneo-cuboid (7), naviculo-cuneiform (4). The secondary radiographic signs were studied for each foot. In the conservative group, 2 patients degraded their clinical status, one developed a spastic flat foot. In the surgical group, all except 2 patients had good clinical and functional results. One patient had

  20. On Heels and Toes: How Ants Climb with Adhesive Pads and Tarsal Friction Hair Arrays.

    Science.gov (United States)

    Endlein, Thomas; Federle, Walter

    2015-01-01

    Ants are able to climb effortlessly on vertical and inverted smooth surfaces. When climbing, their feet touch the substrate not only with their pretarsal adhesive pads but also with dense arrays of fine hairs on the ventral side of the 3rd and 4th tarsal segments. To understand what role these different attachment structures play during locomotion, we analysed leg kinematics and recorded single-leg ground reaction forces in Weaver ants (Oecophylla smaragdina) climbing vertically on a smooth glass substrate. We found that the ants engaged different attachment structures depending on whether their feet were above or below their Centre of Mass (CoM). Legs above the CoM pulled and engaged the arolia ('toes'), whereas legs below the CoM pushed with the 3rd and 4th tarsomeres ('heels') in surface contact. Legs above the CoM carried a significantly larger proportion of the body weight than legs below the CoM. Force measurements on individual ant tarsi showed that friction increased with normal load as a result of the bending and increasing side contact of the tarsal hairs. On a rough sandpaper substrate, the tarsal hairs generated higher friction forces in the pushing than in the pulling direction, whereas the reverse effect was found on the smooth substrate. When the tarsal hairs were pushed, buckling was observed for forces exceeding the shear forces found in climbing ants. Adhesion forces were small but not negligible, and higher on the smooth substrate. Our results indicate that the dense tarsal hair arrays produce friction forces when pressed against the substrate, and help the ants to push outwards during horizontal and vertical walking.

  1. On Heels and Toes: How Ants Climb with Adhesive Pads and Tarsal Friction Hair Arrays.

    Directory of Open Access Journals (Sweden)

    Thomas Endlein

    Full Text Available Ants are able to climb effortlessly on vertical and inverted smooth surfaces. When climbing, their feet touch the substrate not only with their pretarsal adhesive pads but also with dense arrays of fine hairs on the ventral side of the 3rd and 4th tarsal segments. To understand what role these different attachment structures play during locomotion, we analysed leg kinematics and recorded single-leg ground reaction forces in Weaver ants (Oecophylla smaragdina climbing vertically on a smooth glass substrate. We found that the ants engaged different attachment structures depending on whether their feet were above or below their Centre of Mass (CoM. Legs above the CoM pulled and engaged the arolia ('toes', whereas legs below the CoM pushed with the 3rd and 4th tarsomeres ('heels' in surface contact. Legs above the CoM carried a significantly larger proportion of the body weight than legs below the CoM. Force measurements on individual ant tarsi showed that friction increased with normal load as a result of the bending and increasing side contact of the tarsal hairs. On a rough sandpaper substrate, the tarsal hairs generated higher friction forces in the pushing than in the pulling direction, whereas the reverse effect was found on the smooth substrate. When the tarsal hairs were pushed, buckling was observed for forces exceeding the shear forces found in climbing ants. Adhesion forces were small but not negligible, and higher on the smooth substrate. Our results indicate that the dense tarsal hair arrays produce friction forces when pressed against the substrate, and help the ants to push outwards during horizontal and vertical walking.

  2. Morphology and structure of the tarsal glands of the stingless bee Melipona seminigra

    Science.gov (United States)

    Jarau, Stefan; Hrncir, Michael; Zucchi, Ronaldo; Barth, Friedrich G.

    2005-03-01

    Footprint secretions deposited at the nest entrance or on food sources are used for chemical communication by honey bees, bumble bees, and stingless bees. The question of the glandular origin of the substances involved, however, has not been unequivocally answered yet. We investigated the morphology and structure of tarsal glands within the fifth tarsomeres of the legs of workers of Melipona seminigra in order to clarify their possible role in the secretion of footprints. The tarsal gland is a sac-like fold forming a reservoir. Its glandular tissue is composed of a unicellular layer of specialized epidermal cells, which cover the thin cuticular intima forming the reservoir. We found that the tarsal glands lack any openings to the outside and therefore conclude that they are not involved in the secretion of footprint substances. The secretion produced accumulates within the gland's reservoir and reaches as far as into the arolium. Thus it is likely that it serves to fill and unfold the arolium during walking to increase adhesion on smooth surfaces, as is known for honey bees and weaver ants.

  3. The value of spiral CT scan on fracture of ankle joint and tarsal bones

    International Nuclear Information System (INIS)

    Li Zhaoli; Liang Jingyin; Pan Zhifeng

    2009-01-01

    Objective: To study the value of spiral CT scan on the fracture of ankle joint and tarsal bones. Methods: 43 cases with the fracture of ankle joint and tarsal bones were collected and analyzed. All the cases were examined by plain film radiography and spiral CT thin slice scan. Multi-planar reformation (MPR), surface shaded display (SSD) and other techniques of image post-processing were performed in 35 cases of them. Results: Spiral CT scan could demonstrate more fractures than plain film radiography in 28 cases(65.1%). There are 15 cases (34.9%) which are normal in plain film radiography but abnormal in Spiral CT scan. Spiral CT could demonstrate the different length, width, direction and number of linear low density shadow. SSD and MPR were performed again in the cases with avulsion fracture and fragmental fracture to demonstrate the fracture direction and the shape, size and location of fragments more clearly. Conclusion: Spiral CT thin slice scan with image post-processing techniques can play an important role in fracture of ankle joint and tarsal bones. (authors)

  4. Acute cerebellitis successfully managed with temporary cerebrospinal fluid diversion using a long tunnel external ventricular drain: a long-term radiological follow-up of two cases

    Science.gov (United States)

    Waqas, Muhammad; Hadi, Yousaf Bashir; Sheikh, Sadaf; Shamim, Shahzad M

    2016-01-01

    Acute cerebellitis (AC) is a rare inflammatory childhood disorder. Although there is no consensus on standard treatment for cerebellitis, its outcome is usually favourable. We report two cases of AC in the paediatric age group, successfully managed with long tunnel external ventricular drain (EVD). The first patient was an 8-year-old boy with a history of fever and headache. Sequential MRI showed diffuse cerebellar swelling with tonsillar herniation and resulting hydrocephalus. The second patient was a 6-month-old boy who presented with high-grade fever associated with chills. CT scan of the head showed triventricular hydrocephalus with obliteration of cerebrospinal fluid spaces and cisterns. Both patients underwent immediate emergency right-sided long tunnel EVD insertion. The EVD was removed on the 9th day in the first patient and the 10th day in the second patient; the patients showed no neurological deficits at a follow-up of 2 years and 1 year, respectively. PMID:27166004

  5. Acute effect of topical menthol on chronic pain in slaughterhouse workers with carpal tunnel syndrome: triple-blind, randomized placebo-controlled trial

    DEFF Research Database (Denmark)

    Sundstrup, Emil; Jakobsen, Markus Due; Brandt, Mikkel

    2014-01-01

    Topical menthol gels are classified "topical analgesics" and are claimed to relieve minor aches and pains of the musculoskeletal system. In this study we investigate the acute effect of topical menthol on carpal tunnel syndrome (CTS). We screened 645 slaughterhouse workers and recruited 10...... participants with CTS and chronic pain of the arm/hand who were randomly distributed into two groups to receive topical menthol (Biofreeze) or placebo (gel with a menthol scent) during the working day and 48 hours later the other treatment (crossover design). Participants rated arm/hand pain intensity during...... the last hour of work (scale 0-10) immediately before 1, 2, and 3 hours after application. Furthermore, global rating of change (GROC) in arm/hand pain was assessed 3 hours after application. Compared with placebo, pain intensity and GROC improved more following application of topical menthol (P = 0...

  6. Acute Effect of Topical Menthol on Chronic Pain in Slaughterhouse Workers with Carpal Tunnel Syndrome: Triple-Blind, Randomized Placebo-Controlled Trial

    Directory of Open Access Journals (Sweden)

    Emil Sundstrup

    2014-01-01

    Full Text Available Topical menthol gels are classified “topical analgesics” and are claimed to relieve minor aches and pains of the musculoskeletal system. In this study we investigate the acute effect of topical menthol on carpal tunnel syndrome (CTS. We screened 645 slaughterhouse workers and recruited 10 participants with CTS and chronic pain of the arm/hand who were randomly distributed into two groups to receive topical menthol (Biofreeze or placebo (gel with a menthol scent during the working day and 48 hours later the other treatment (crossover design. Participants rated arm/hand pain intensity during the last hour of work (scale 0–10 immediately before 1, 2, and 3 hours after application. Furthermore, global rating of change (GROC in arm/hand pain was assessed 3 hours after application. Compared with placebo, pain intensity and GROC improved more following application of topical menthol (P=0.026 and P=0.044, resp.. Pain intensity of the arm/hand decreased by −1.2 (CI 95%: −1.7 to −0.6 following topical menthol compared with placebo, corresponding to a moderate effect size of 0.63. In conclusion, topical menthol acutely reduces pain intensity during the working day in slaughterhouse workers with CTS and should be considered as an effective nonsystemic alternative to regular analgesics in the workplace management of chronic and neuropathic pain.

  7. The Tarsal Bone Test: A Basic Test of Health Sciences Students' Knowledge of Lower Limb Anatomy

    Directory of Open Access Journals (Sweden)

    José Manuel Castillo-López

    2014-01-01

    Full Text Available Objectives. The aim of the present study was to design an easy-to-use tool, the tarsal bone test (TBT, to provide a snapshot of podiatry students’ basic anatomical knowledge of the bones of the lower limb. Methods. The study included 254 podiatry students from three different universities, 145 of them were first-year students and 109 were in their fourth and final years. The TBT was administered without prior notice to the participants and was to be completed in 5 minutes. Results. The results show that 97.2% of the subjects (n=247 correctly labelled all tarsal bones, while the other 2.8% (n=7 incorrectly labelled at least one bone, that was either the cuboid (7 times or the navicular (6 times. Although only one fourth-year student inaccurately identified one bone, no significant differences in the distribution of the correct and incorrect responses were found between first and fourth-year students. Conclusions. The TBT seems to be a straightforward and easy-to-apply instrument, and provides an objective view of the level of knowledge acquired at different stages of podiatry studies.

  8. Tunneling works. Tunnel koji

    Energy Technology Data Exchange (ETDEWEB)

    Higo, M [Hazam Gumi, Ltd., Tokyo (Japan)

    1991-10-25

    A mountain tunneling method for rock-beds used to be applied mainly to construction works in the mountains under few restrictions by environmental problems. However, construction works near residential sreas have been increasing. There are such enviromental problems due to tunneling works as vibration, noise, lowering of ground-water level, and influences on other structures. This report mainly describes the measurement examples of vibration and noise accompanied with blasting and the effects of the measures to lessen such influences. When the tunneling works for the railroad was carried out on the natural ground mainly composed of basalt, vibration of the test blasting was measured at three stations with piezoelectric accelerometers. Then, ordinary blasting, mutistage blasting, and ABM blasting methods were used properly besed on the above results, and only a few complaints were made. In the different works, normal noise and low-frequency sound were mesured at 22 stations around the pit mouth. As countermeasures for noise, sound-proof sheets, walls, and single and double doors were installed and foundto be effective. 1 ref., 6 figs., 1 tab.

  9. External fixation to correct tarsal-metatarsal fracture in rock pigeon (Columba livia

    Directory of Open Access Journals (Sweden)

    Leandro Almeida Rui

    Full Text Available ABSTRACT Orthopedic conditions, such as bone fractures, are very common in avian medicine. External fixators have been considered the gold standard for birds, since they allow early movement of the limbs and minimal invasive surgery. Fractures in several bones have been successfully treated in pigeons. However, to the best of our knowledge, this case represents the first report of successful surgical repair of tarsal-metatarsal fracture in rock pigeon. External fixator was made with four 24G catheters, being inserted manually proximal and distal to the fracture and connected with polymerizable acrylic. Radiographic consolidation of fracture was observed 60 days post-surgery and anti-inflammatory and antibiotic protocols were successful on avoiding pain and infection during surgery and bone healing.

  10. Influence of free-stall base on tarsal joint lesions and hygiene in dairy cows.

    Science.gov (United States)

    Fulwider, W K; Grandin, T; Garrick, D J; Engle, T E; Lamm, W D; Dalsted, N L; Rollin, B E

    2007-07-01

    The objective was to quantify the incidence of tarsal lesions and level of hygiene by stall bed type. Cows were scored on 100 dairies from Wisconsin, Minnesota, Indiana, Iowa, and New York in the fall and winter. Thirty-eight dairies used rubber-filled mattresses (RFM), 27 had sand beds, 29 had waterbeds, and 6 used compost packs (CPk). Stocking density, stall dimensions, bedding amount, bedding frequency, and type of bedding were recorded. One pen of early-lactation multiparous cows on each dairy was scored based on injury of the tarsal joints at the lateral and medial surfaces and tuber calcis at the dorsal, lateral, and medial surfaces. A tarsal score of 1 represented hair loss, 2 was moderate, and 3 indicated severe swelling. Differences between bed types in the percentages of cows with lesions were tested with one-way ANOVA by lesion severity and incidence, with farm as the experimental unit. Cows on sand beds or waterbeds had fewer lesion scores of 1, 2, and 3 than those on RFM. The percentages of score 1 were 54.6 +/- 4.4 (RFM), 22.5 +/- 4.7 (sand), and 29.8 +/- 4.3 (waterbed), whereas the percentages of score 2 were 14.0 +/- 1.4, 2.3 +/- 1.5, and 5.0 +/- 1.4, and of score 3 were 3.0 +/- 0.4, 0.2 +/- 0.4, and 0.4 +/- 0.4. Cows on CPk had no lesions. Hygiene scores ranged from 1 to 5, with 1 being clean and 5 soiled. The percentages of hygiene score 1 were 0 (compost), 0.4 (RFM), 0.4 (sand), and 0.4 (waterbeds); those with score 2 were 79.0, 84.0 +/- 0.01, 73.2 +/- 0.01, and 80.4 +/- 0.01; with score 3 were 20.3, 15.2 +/- 0.01, 23.8 +/- 0.01, and 18.6 +/- 0.01; with score 4 were 0.8, 0.005 +/- 0.001, 0.006 +/- 0.001, and 0.025 +/- 0.003; and with score 5 was 0 for all bed types. Cows on RFM and waterbeds had improved hygiene compared with cows on sand beds. There was no difference in somatic cell count (SCC) by bed type. The percentage of cows in fourth lactation or greater on waterbeds (19.8 +/- 1.8) was greater than those on RFM (13.3 +/- 1.6) or on sand

  11. Morphology and neurophysiology of tarsal vibration receptors in the water strider Aquarius paludum (Heteroptera: Gerridae).

    Science.gov (United States)

    Perez Goodwyn, Pablo; Katsumata-Wada, Ayako; Okada, Koutaroh

    2009-09-01

    Substrate vibratory information receptors are extensively studied in insects and spiders, however for water surface dwelling species little data is available. We studied the vibration receptive organs in tarsi of the water strider Aquarius paludum, using light, transmission and scanning electron microscopes, and recorded the neural activity of the organs in response to vibrational stimuli, which were afterwards analysed with a custom made spike sorting program. We found that the tarsal chordotonal organ has one set of three scoloparia: one in the tarsomere I and two in the tarsomere II, all of which consisted of a few scolopidia. The chordotonal organ clearly responded to vibratory stimulation. Furthermore, we found that a pair of large subapical emergent dorsal setae, which had been deemed mechanosensory by previous authors, are not so. In turn, four ventral subapical trichobothria that are in direct contact with the water surface during locomotion, proved to be mechanosensory. The anatomical and ultrastructural observations support these electro-physiological results.

  12. Diagnostic imaging of the equine tarsal region using radiography and ultrasonography. Part 1: the soft tissues.

    Science.gov (United States)

    Vanderperren, Katrien; Raes, Els; Hoegaerts, Michel; Saunders, Jimmy H

    2009-02-01

    The equine tarsus is the most commonly affected hindlimb region associated with lameness. Diagnostic imaging is routinely applied but because of its complexity, being composed of 10 multifaceted bones and different joints, multiple ligaments, tendons and bursae, imaging this region can be a challenge. This is the first part of a two-part review of the structures and disorders of the equine tarsus. It describes the principal disorders affecting the soft tissues of the tarsal region and addresses some of the technical aspects in taking radiographic, ultrasonographic and scintigraphic images of the different soft tissue lesions. Where applicable, comments on the diagnostic use of contrast radiography, arthroscopy and tenoscopy are made. In current clinical practice a combination of radiography and ultrasonography is still most frequently used to arrive at a diagnosis.

  13. Pronounced variation in tarsal and foot feathering in the upland buzzard (Buteo hemilasius) in Mongolia

    Science.gov (United States)

    Ellis, D.H.; Woffinden, N.; Whitlock, P.L.; Tsengeg, Pu

    1999-01-01

    During 1994, 1995, 1997, and 1998 expeditions across Mongolia, we located over 250 upland buzzard (Buteo hemilasius) nests. At these, we noted considerable morphological variation in plumage coloration and in leg pterylosis. In 1997 and 1998, we examined 131 nests scattered across eastern and central Mongolia and report here the tarsal condition of 119 nestlings from 59 broods where young were at least 2 weeks of age. Of 119 birds carefully examined, 50 (42%) had less than fully feathered tarsi and 4 of the 69 with fully feathered tarsi had scattered feathers on their toes. Thus, 54 of 119 birds (45%) in some way deviated from the feathered tarsibare toes condition. This extraordinary degree of variability in feather patterns may be best explained as the result of extensive and relatively recent hybridization between the longlegged (Buteo rufinus) and roughlegged (B. lagopus) buzzards and/or between long-legged and upland buzzards.

  14. Primate tarsal bones from Egerkingen, Switzerland, attributable to the middle Eocene adapiform Caenopithecus lemuroides.

    Science.gov (United States)

    Seiffert, Erik R; Costeur, Loïc; Boyer, Doug M

    2015-01-01

    The middle Eocene species Caenopithecus lemuroides, known solely from the Egerkingen fissure fillings in Switzerland, was the first Paleogene fossil primate to be correctly identified as such (by Ludwig Rütimeyer in 1862), but has long been represented only by fragmentary mandibular and maxillary remains. More recent discoveries of adapiform fossils in other parts of the world have revealed Caenopithecus to be a biogeographic enigma, as it is potentially more closely related to Eocene adapiforms from Africa, Asia, and North America than it is to any known European forms. More anatomical evidence is needed, however, to provide robust tests of such phylogenetic hypotheses. Here we describe and analyze the first postcranial remains that can be attributed to C. lemuroides-an astragalus and three calcanei held in the collections of the Naturhistorisches Museum Basel that were likely recovered from Egerkingen over a century ago. Qualitative and multivariate morphometric analyses of these elements suggest that C. lemuroides was even more loris-like than European adapines such as Adapis and Leptadapis, and was not simply an adapine with an aberrant dentition. The astragalus of Caenopithecus is similar to that of younger Afradapis from the late Eocene of Egypt, and parsimony and Bayesian phylogenetic analyses that include the new tarsal data strongly support the placement of Afradapis and Caenopithecus as sister taxa to the exclusion of all other known adapiforms, thus implying that dispersal between Europe and Africa occurred during the middle Eocene. The new tarsal evidence, combined with previously known craniodental fossils, allows us to reconstruct C. lemuroides as having been an arboreal and highly folivorous 1.5-2.5 kg primate that likely moved slowly and deliberately with little or no capacity for acrobatic leaping, presumably maintaining consistent powerful grasps on branches in both above-branch and inverted postures.

  15. Reconstruction of fingers after electrical injury using lateral tarsal artery flap

    Directory of Open Access Journals (Sweden)

    Zhang MH

    2017-07-01

    Full Text Available Minghua Zhang, Mitao Huang, Pihong Zhang, Pengfei Liang, Licheng Ren, Jizhang Zeng, Jie Zhou, Xiong Liu, Tinghong Xie, Xiaoyuan Huang Department of Burns Reconstruction Surgery, Xiangya Hospital, Central South University, Changsha, Hunan, People’s Republic of China Objective: Electrical injuries to the fingers account for the majority of total severe burns that occur each year. While several types of flaps have been used in covering finger defects, all have limitations or disadvantages. The purpose of this study was to introduce our clinical experiences of using the lateral tarsal artery (LTA flap to successfully restore fingers after electrical injury.Patients and methods: From 2005 to 2012, 10 patients with 14 severe electrical burns to their fingers, including six thumbs and four index and four middle fingers, were treated with LTA flap. The wound size ranged from 2.0×3.0 cm to 3.5×5.0 cm. The flap with free tendon graft was used to repair the tendon defect in four cases, free nerve graft was used to repair the feeling defect in two cases, and the flap with nerve was used to repair the feeling defect in two cases. All the patients were followed up for 3 months to 2 years.Results: All skin flaps adhered successfully and there were no complications. All patients were satisfied with the esthetic appearance and functional outcome of the finger reconstruction.Conclusion: LTA flap is a reliable method to restore fingers after severe electrical injuries. Keywords: electrical injuries to fingers, lateral tarsal artery flap

  16. Central tarsal bone fractures in horses not used for racing: Computed tomographic configuration and long-term outcome of lag screw fixation

    OpenAIRE

    Gunst, S; Del Chicca, Francesca; Fürst, Anton; Kuemmerle, Jan M

    2016-01-01

    REASONS FOR PERFORMING STUDY: There are no reports on the configuration of equine central tarsal bone fractures based on cross-sectional imaging and clinical and radiographic long-term outcome after internal fixation. OBJECTIVES: To report clinical, radiographic and computed tomographic findings of equine central tarsal bone fractures and to evaluate the long-term outcome of internal fixation. STUDY DESIGN: Retrospective case series. METHODS: All horses diagnosed with a central tarsa...

  17. Slab fractures of the third tarsal bone: Minimally invasive repair using a single 3.5 mm cortex screw placed in lag fashion in 17 Thoroughbred racehorses.

    Science.gov (United States)

    Barker, W H J; Wright, I M

    2017-03-01

    A technique for minimally invasive repair of slab fractures of the third tarsal bone has not previously been reported. Results of third tarsal bone slab fracture repair in Thoroughbred racehorses are lacking. To report the outcomes of repair of uniplanar frontal slab factures of the third tarsal bone using a single 3.5 mm cortex screw in lag fashion. Retrospective case series. Case records of horses that had undergone this procedure were reviewed. Seventeen horses underwent surgery. Eighteen percent of cases had wedge shaped third tarsal bones. A point midway between the long and lateral digital extensor tendons and centrodistal and tarsometatarsal joints created a suitable entry site for implants. The fracture location, configuration and curvature of the third tarsal bone and associated joints requires a dorsolateral proximal-plantaromedial distal trajectory for the screw, which was determined by preplaced needles. There were no complications and fractures healed in all cases at 4-6 months post surgery. Seventy-nine percent of horses returned to racing and, at the time of reporting, 3 are in post operative rehabilitation programmes. The technique reported provides a safe, appropriate and repeatable means of repairing slab fractures of the third tarsal bone. Surgical repair is a viable alternative to conservative management. © 2016 EVJ Ltd.

  18. Tarsal morphology of the pleuraspidotheriid mammal Hilalia from the middle Eocene of Turkey

    Directory of Open Access Journals (Sweden)

    Gregoire Metais

    2017-03-01

    Full Text Available Pleuraspidotheriids are a group of primitive ungulate mammals that, until recently, were thought to be restricted to the late Paleocene of Western Europe. It has been hypothesized that this family actually survived in Central Anatolia until at least the middle Eocene. However, these anachronistically young Anatolian “survivors”, including the genus Hilalia, were previously documented mainly by dental remains. Here, we describe the previously unknown astragalus of Hilalia saribeya, which confirms the pleuraspidotheriid affinities of the genus, and supports phylogenetic reconstructions that place Hilalia as the sister group of Pleuraspidotherium. The morphology of the astragalus suggests sub-cursorial plantigrade locomotion for H. saribeya, although its tarsal morphology remains generalized enough that scansorial capabilities cannot be ruled out. The evolution of Hilalia is addressed in the context of the apparent geographic isolation of Central Anatolia during the Eocene. The endemic character of the mammalian fauna of Central Anatolia during the middle Eocene emphasizes how the complex paleogeography of the northern margin of Neotethys impacted local biotas in a region situated at the crossroads of very distinctive biogeographic zones.

  19. Oldest known euarchontan tarsals and affinities of Paleocene Purgatorius to Primates.

    Science.gov (United States)

    Chester, Stephen G B; Bloch, Jonathan I; Boyer, Doug M; Clemens, William A

    2015-02-03

    Earliest Paleocene Purgatorius often is regarded as the geologically oldest primate, but it has been known only from fossilized dentitions since it was first described half a century ago. The dentition of Purgatorius is more primitive than those of all known living and fossil primates, leading some researchers to suggest that it lies near the ancestry of all other primates; however, others have questioned its affinities to primates or even to placental mammals. Here we report the first (to our knowledge) nondental remains (tarsal bones) attributed to Purgatorius from the same earliest Paleocene deposits that have yielded numerous fossil dentitions of this poorly known mammal. Three independent phylogenetic analyses that incorporate new data from these fossils support primate affinities of Purgatorius among euarchontan mammals (primates, treeshrews, and colugos). Astragali and calcanei attributed to Purgatorius indicate a mobile ankle typical of arboreal euarchontan mammals generally and of Paleocene and Eocene plesiadapiforms specifically and provide the earliest fossil evidence of arboreality in primates and other euarchontan mammals. Postcranial specializations for arboreality in the earliest primates likely played a key role in the evolutionary success of this mammalian radiation in the Paleocene.

  20. Decaleside: a new class of natural insecticide targeting tarsal gustatory sites

    Science.gov (United States)

    Rajashekar, Yallappa; Rao, Lingamallu J. M.; Shivanandappa, Thimmappa

    2012-10-01

    Natural sources for novel insecticide molecules hold promise in view of their eco-friendly nature, selectivity, and mammalian safety. Recent progress in understanding the biology of insect olfaction and taste offers new strategies for developing selective pest control agents. We have isolated two natural insecticidal molecules from edible roots of Decalepis hamiltonii named Decalesides I and II, which are novel trisaccharides, highly toxic to household insect pests and stored-product insects. We have experimentally shown that insecticidal activity requires contact with tarsi on the legs but is not toxic orally. The insecticidal activity of molecules is lost by hydrolysis, and various sugars modify toxic response, showing that the insecticidal activity is via gustatory sites on the tarsi. Selective toxicity to insects by virtue of their gustatory site of action and the mammalian safety of the new insecticides is inherent in their chemical structure with 1-4 or 1-1 α linkage that is easily hydrolyzed by digestive enzymes of mammals. Decalesides represent a new chemical class of natural insecticides with a unique mode of action targeting tarsal chemosensory/gustatory system of insects.

  1. Central tarsal bone fractures in horses not used for racing: Computed tomographic configuration and long-term outcome of lag screw fixation.

    Science.gov (United States)

    Gunst, S; Del Chicca, F; Fürst, A E; Kuemmerle, J M

    2016-09-01

    There are no reports on the configuration of equine central tarsal bone fractures based on cross-sectional imaging and clinical and radiographic long-term outcome after internal fixation. To report clinical, radiographic and computed tomographic findings of equine central tarsal bone fractures and to evaluate the long-term outcome of internal fixation. Retrospective case series. All horses diagnosed with a central tarsal bone fracture at our institution in 2009-2013 were included. Computed tomography and internal fixation using lag screw technique was performed in all patients. Medical records and diagnostic images were reviewed retrospectively. A clinical and radiographic follow-up examination was performed at least 1 year post operatively. A central tarsal bone fracture was diagnosed in 6 horses. Five were Warmbloods used for showjumping and one was a Quarter Horse used for reining. All horses had sagittal slab fractures that began dorsally, ran in a plantar or plantaromedial direction and exited the plantar cortex at the plantar or plantaromedial indentation of the central tarsal bone. Marked sclerosis of the central tarsal bone was diagnosed in all patients. At long-term follow-up, 5/6 horses were sound and used as intended although mild osteophyte formation at the distal intertarsal joint was commonly observed. Central tarsal bone fractures in nonracehorses had a distinct configuration but radiographically subtle additional fracture lines can occur. A chronic stress related aetiology seems likely. Internal fixation of these fractures based on an accurate diagnosis of the individual fracture configuration resulted in a very good prognosis. © 2015 EVJ Ltd.

  2. Three-dimensional analysis of tarsal bone response to axial loading in patients with hallux valgus and normal feet.

    Science.gov (United States)

    Watanabe, Kota; Ikeda, Yasutoshi; Suzuki, Daisuke; Teramoto, Atsushi; Kobayashi, Takuma; Suzuki, Tomoyuki; Yamashita, Toshihiko

    2017-02-01

    Patients with hallux valgus present a variety of symptoms that may be related to the type of deformity. Weightbearing affects the deformities, and the evaluation of the load response of tarsal bones has been mainly performed using two-dimensional plane radiography. The purpose of this study was to investigate and compare structural changes in the medial foot arch between patients with hallux valgus and normal controls using a computer image analysis technique and weightbearing computed tomography data. Eleven patients with hallux valgus and eleven normal controls were included. Computed tomograms were obtained with and without simulated weightbearing using a compression device. Computed tomography data were transferred into a personal computer, and a three-dimensional bone model was created using image analysis software. The load responses of each tarsal bone in the medial foot arch were measured three-dimensionally and statistically compared between the two groups. Displacement of each tarsal bone under two weightbearing conditions was visually observed by creating three-dimensional bone models. At the first metatarsophalangeal joint, the proximal phalanges of the hallux valgus group showed significantly different displacements in multiple directions. Moreover, opposite responses to axial loading were also observed in both translation and rotation between the two groups. Weightbearing caused deterioration of the hallux valgus deformity three-dimensionally at the first metatarsophalangeal joint. Information from the computer image analysis was useful for understanding details of the pathology of foot disorders related to the deformities or instability and may contribute to the development of effective conservative and surgical treatments. Copyright © 2017 Elsevier Ltd. All rights reserved.

  3. Tarsal taste neuron activity and proboscis extension reflex in response to sugars and amino acids in Helicoverpa armigera (Hubner).

    Science.gov (United States)

    Zhang, Yun-Feng; van Loon, Joop J A; Wang, Chen-Zhu

    2010-08-15

    In adult female Helicoverpa armigera (Hübner), the fifth tarsomere of the prothoracic legs bears 14 gustatory trichoid chemosensilla. These chemosensilla were characterized through electrophysiological experiments by stimulating with sucrose, glucose, fructose, maltose, myo-inositol and 20 common amino acids. In electrophysiological recordings from nine sensilla, responses were obtained to certain compounds tested at 100 mmol l(-1), and the response spectra differed from broad to narrow. The four sugars excited the same receptor neuron in sensillum a and sensillum b; sucrose and myo-inositol, sucrose and lysine, myo-inositol and lysine excited two different receptor neurons respectively in sensillum a; fructose and lysine excited two different receptor neurons in sensillum n. Furthermore, the four sugars, myo-inositol and lysine all elicited concentration-dependent electrophysiological responses. These six compounds also induced the proboscis extension reflex (PER) followed by ingestion of the solution when they were applied on the tarsi. Lysine and sucrose caused the strongest electrophysiological responses. However, sucrose had the strongest stimulatory effect on the PER whereas lysine had the weakest. Mixtures of sucrose with the other sugars or with lysine had a similar stimulatory effect on the PER as sucrose alone. The electrophysiological and behavioural responses caused by a range of sucrose concentrations were positively correlated. We conclude that the tarsal gustatory sensilla play an essential role in perceiving sugars available in floral nectar and provide chemosensory information determining feeding behaviour. Tarsal taste-receptor-neuron responses to lysine are implicated in oviposition behaviour.

  4. Recognition tunneling

    Czech Academy of Sciences Publication Activity Database

    Lindsay, S.; He, J.; Sankey, O.; Hapala, Prokop; Jelínek, Pavel; Zhang, P.; Chang, S.; Huang, S.

    2010-01-01

    Roč. 21, č. 26 (2010), 262001/1-262001/12 ISSN 0957-4484 R&D Projects: GA ČR GA202/09/0545 Institutional research plan: CEZ:AV0Z10100521 Keywords : STM * tunneling current * molecular electronics * DFT calculations Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.644, year: 2010

  5. Tunnel - history of

    International Nuclear Information System (INIS)

    1998-11-01

    This book introduces history of tunnel in ancient times, the middle ages and modern times, survey of tunnel and classification of bedrock like environment survey of position, survey of the ground, design of tunnel on basic thing of the design, and design of tunnel of bedrock, analysis of stability of tunnel and application of the data, construction of tunnel like lattice girder and steel fiber reinforced shot crete, and maintenance control and repair of tunnel.

  6. MR imaging of the carpal tunnel syndrome

    International Nuclear Information System (INIS)

    Elias, D.; Lind, J.; Blair, S.; Light, T.; Wisniewski, R.; Moncado, R.

    1987-01-01

    MR is an ideal noninvasive means to image the structures forming the carpal tunnel in both normal and pathologic conditions. The carpal tunnel syndrome is a frequently encountered entity caused by compression of the median nerve as it passes through the carpal tunnel. This may result from a variety of conditions including edema from acute chronic trauma, rheumatoid tenosynovitis, degenerative joint disease or soft-tissue masses. This exhibit demonstrates the optimal MR imaging techniques to display the structures of the carpal tunnel. The normal anatomy is reviewed and variations in normal anatomy that may predispose to disease are included. Examples of the morphologic changes demonstrated in 20 patients diagnosed with carpal tunnel syndrome are displayed. The exhibit also reviews the findings in 20 postoperative cases

  7. Osteochondral lesions in distal tarsal joints of Icelandic horses reveal strong associations between hyaline and calcified cartilage abnormalities

    Directory of Open Access Journals (Sweden)

    CJ Ley

    2014-03-01

    Full Text Available Osteochondral lesions in the joints of the distal tarsal region of young Icelandic horses provide a natural model for the early stages of osteoarthritis (OA in low-motion joints. We describe and characterise mineralised and non-mineralised osteochondral lesions in left distal tarsal region joint specimens from twenty-two 30 ±1 month-old Icelandic horses. Combinations of confocal scanning light microscopy, backscattered electron scanning electron microscopy (including, importantly, iodine staining and three-dimensional microcomputed tomography were used on specimens obtained with guidance from clinical imaging. Lesion-types were described and classified into groups according to morphological features. Their locations in the hyaline articular cartilage (HAC, articular calcified cartilage (ACC, subchondral bone (SCB and the joint margin tissues were identified and their frequency in the joints recorded. Associations and correlations between lesion-types were investigated for centrodistal joints only. In centrodistal joints the lesion-types HAC chondrocyte loss, HAC fibrillation, HAC central chondrocyte clusters, ACC arrest and ACC advance had significant associations and strong correlations. These lesion-types had moderate to high frequency in centrodistal joints but low frequencies in tarsometatarsal and talocalcaneal-centroquartal joints. Joint margin lesion-types had no significant associations with other lesion-types in the centrodistal joints but high frequency in both the centrodistal and tarsometatarsal joints. The frequency of SCB lesion-types in all joints was low. Hypermineralised infill phase lesion-types were detected. Our results emphasise close associations between HAC and ACC lesions in equine centrodistal joints and the importance of ACC lesions in the development of OA in low-motion compression-loaded equine joints.

  8. Osteochondral lesions in distal tarsal joints of Icelandic horses reveal strong associations between hyaline and calcified cartilage abnormalities.

    Science.gov (United States)

    Ley, C J; Ekman, S; Hansson, K; Björnsdóttir, S; Boyde, A

    2014-03-25

    Osteochondral lesions in the joints of the distal tarsal region of young Icelandic horses provide a natural model for the early stages of osteoarthritis (OA) in low-motion joints. We describe and characterise mineralised and non-mineralised osteochondral lesions in left distal tarsal region joint specimens from twenty-two 30 ±1 month-old Icelandic horses. Combinations of confocal scanning light microscopy, backscattered electron scanning electron microscopy (including, importantly, iodine staining) and three-dimensional microcomputed tomography were used on specimens obtained with guidance from clinical imaging. Lesion-types were described and classified into groups according to morphological features. Their locations in the hyaline articular cartilage (HAC), articular calcified cartilage (ACC), subchondral bone (SCB) and the joint margin tissues were identified and their frequency in the joints recorded. Associations and correlations between lesion-types were investigated for centrodistal joints only. In centrodistal joints the lesion-types HAC chondrocyte loss, HAC fibrillation, HAC central chondrocyte clusters, ACC arrest and ACC advance had significant associations and strong correlations. These lesion-types had moderate to high frequency in centrodistal joints but low frequencies in tarsometatarsal and talocalcaneal-centroquartal joints. Joint margin lesion-types had no significant associations with other lesion-types in the centrodistal joints but high frequency in both the centrodistal and tarsometatarsal joints. The frequency of SCB lesion-types in all joints was low. Hypermineralised infill phase lesion-types were detected. Our results emphasise close associations between HAC and ACC lesions in equine centrodistal joints and the importance of ACC lesions in the development of OA in low-motion compression-loaded equine joints.

  9. Carpal Tunnel Syndrome

    Science.gov (United States)

    ... a passing cramp? It could be carpal tunnel syndrome. The carpal tunnel is a narrow passageway of ... three times more likely to have carpal tunnel syndrome than men. Early diagnosis and treatment are important ...

  10. Tunneling technologies for the collider ring tunnels

    International Nuclear Information System (INIS)

    Frobenius, P.

    1989-01-01

    The Texas site chosen for the Superconducting Super Collider has been studied, and it has been determined that proven, conventional technology and accepted engineering practice are suitable for constructing the collider tunnels. The Texas National Research Laboratory Commission report recommended that two types of tunneling machines be used for construction of the tunnels: a conventional hard rock tunnel boring machine (TBM) for the Austin chalk and a double shielded, rotary TBM for the Taylor marl. Since the tunneling machines usually set the pace for the project, efficient planning, operation, and coordination of the tunneling system components will be critical to the schedule and cost of the project. During design, tunneling rate prediction should be refined by focusing on the development of an effective tunneling system and evaluating its capacity to meet or exceed the required schedules. 8 refs., 13 figs

  11. Reconstruction of large upper eyelid defects with a free tarsal plate graft and a myocutaneous pedicle flap plus a free skin graft.

    Science.gov (United States)

    Toft, Peter B

    2016-01-01

    To review and present the results of a one-step method employing a free tarsal plate graft and a myocutaneous pedicle flap plus a free skin graft for reconstruction of large upper eyelid defects after tumour surgery. This was a retrospective case-series of 8 patients who underwent reconstruction of the upper eyelid after tumour removal. The horizontal defect involved 50-75% of the lid (3 pts.), more than 75% (3 pts.), and more than 75% plus the lateral canthus (2 pts.). The posterior lamella was reconstructed with contralateral upper eyelid tarsal plate. The anterior lamella was reconstructed with a laterally based myocutaneous pedicle flap in 7 patients, leaving a raw surface under the brow which was covered with a free skin graft. In 1 patient with little skin left under the brow, the anterior lamella was reconstructed with a bi-pedicle orbicularis muscle flap together with a free skin graft. All patients healed without necrosis, did not suffer from lagophthalmos, achieved reasonable cosmesis, and did not need lubricants. In one patient, a contact lens was necessary for three weeks because of corneal erosion. One patient still needs a contact lens 3 months after excision to avoid eye discomfort. Large upper eyelid defects can be reconstructed with a free tarsal plate graft and a laterally based myocutaneous pedicle flap in combination with a free skin graft. Two-step procedures can probably be avoided in most cases.

  12. Effect of graft shape in lateral column lengthening on tarsal bone position and subtalar and talonavicular contact pressure in a cadaveric flatfoot model.

    Science.gov (United States)

    Campbell, Sean T; Reese, Keri A; Ross, Steven D; McGarry, Michelle H; Leba, Thu-Ba; Lee, Thay Q

    2014-11-01

    Lateral column lengthening (LCL) has been used for correction of flatfoot deformity. The purpose of this study was to determine the effect of LCL graft shape on tarsal bone position and talonavicular and subtalar joint pressure. A flatfoot model was created in 6 cadaveric specimens. Corrective LCL was performed using a rectangular graft or a trapezoidal graft with the broad surface oriented dorsally, laterally, or plantarly. Bony surface markers were digitized to calculate angular parameters used in the evaluation of flatfoot deformity. Contact pressure and area in the subtalar and talonavicular joints were also recorded. All measurements were carried out under multiple axial loads in the intact and flatfoot conditions, and following LCL with each graft shape. Flatfoot creation resulted in significant changes in arch collapse and forefoot abduction. LCL with a rectangular graft best corrected these parameters, while a laterally oriented trapezoidal graft provided some correction. Talonavicular contact pressure was unchanged after flatfoot creation, and was significantly less than intact after LCL. Subtalar contact pressure decreased in some conditions after flatfoot creation, and decreased further after LCL. LCL with a rectangular graft best restored tarsal bone orientation in a cadaveric flatfoot model. The decreases in talonavicular pressure likely represent redistribution of force from the medial to lateral foot. When performing LCL for flatfoot deformity, increased bone graft volume medially better restores tarsal bone position. One way of achieving this is through the use of a rectangular graft as opposed to a trapezoidal graft. © The Author(s) 2014.

  13. 铁路既有隧道维修施工作业急性职业中毒对策研究%Countermeasures against acute occupational poisoning in maintenance construction of existing railway tunnel

    Institute of Scientific and Technical Information of China (English)

    王雷; 惠兆斌

    2013-01-01

    According to the concentrations of carbon monoxide and nitrogen oxides in railway tunnels under 3 construction modes to put forward HACCP and targeted control measures,and make maximum avoidance of acute professional accident.[Methods] The construction of single track tunnel by Kunming Railway Bureau was selected as study object.The concentrations of carbon monoxide,nitrogen dioxide were monitored in the operation spots during construction process,and the data of different construction modes were carried out t test.The risk grade of the 3 kinds of construction was classified on the nitrogen dioxide concentration,and the risk control points were identified on the HACCP principles to develop control measure.[Results] Under the normal construction of 3 different modes,the concentrations of nitrogen dioxide in descending order were artificial ballast cleaning,tamping and track replacement,all meeting national standard; while the concentrations of carbon monoxide in descending order were track replacement,artificial ballast cleaning and artificial ballast cleaning,the concentrations of carbon monoxide in track replacement exceeded 4-12 times of national limits,artificial ballast cleaning over 2 times,but tamping within the national limit.[Conclusion] The simple tamping construction in tunnel belongs to low-risk operation which is unlikely to cause acute carbon monoxide poisoning.Artificial ballast cleaning belongs to medium-risk operation which may cause acute poisoning of carbon monoxide ;the key control point by HACCP is to manage generators and the number of locomotives entering into the tunnel simultaneously.Track replacement belongs to high-risk operation which is easy to cause acute carbon monoxide poisoning; the key control point by HACCP is to manage small bolt machine and generators.The occupational protection on HACCP control points in 3 construction mode based on risk grade from the aspects of organization and management,worker,equipment and protection is

  14. Transonic Dynamics Tunnel (TDT)

    Data.gov (United States)

    Federal Laboratory Consortium — The Transonic Dynamics Tunnel (TDT) is a continuous flow wind-tunnel facility capable of speeds up to Mach 1.2 at stagnation pressures up to one atmosphere. The TDT...

  15. Quantum theory of tunneling

    CERN Document Server

    Razavy, Mohsen

    2014-01-01

    In this revised and expanded edition, in addition to a comprehensible introduction to the theoretical foundations of quantum tunneling based on different methods of formulating and solving tunneling problems, different semiclassical approximations for multidimensional systems are presented. Particular attention is given to the tunneling of composite systems, with examples taken from molecular tunneling and also from nuclear reactions. The interesting and puzzling features of tunneling times are given extensive coverage, and the possibility of measurement of these times with quantum clocks are critically examined. In addition by considering the analogy between evanescent waves in waveguides and in quantum tunneling, the times related to electromagnetic wave propagation have been used to explain certain aspects of quantum tunneling times. These topics are treated in both non-relativistic as well as relativistic regimes. Finally, a large number of examples of tunneling in atomic, molecular, condensed matter and ...

  16. Road and Railroad Tunnels

    Data.gov (United States)

    Department of Homeland Security — Tunnels in the United States According to the HSIP Tiger Team Report, a tunnel is defined as a linear underground passageway open at both ends. This dataset is based...

  17. Hypersonic Tunnel Facility (HTF)

    Data.gov (United States)

    Federal Laboratory Consortium — The Hypersonic Tunnel Facility (HTF) is a blow-down, non-vitiated (clean air) free-jet wind tunnel capable of testing large-scale, propulsion systems at Mach 5, 6,...

  18. Proton tunneling in solids

    Energy Technology Data Exchange (ETDEWEB)

    Kondo, J.

    1998-10-01

    The tunneling rate of the proton and its isotopes between interstitial sites in solids is studied theoretically. The phonons and/or the electrons in the solid have two effects on the tunneling phenomenon. First, they suppress the transfer integral between two neighbouring states. Second, they give rise to a finite lifetime of the proton state. Usually the second effect is large and the tunneling probability per unit time (tunneling rate) can be defined. In some cases, however, a coherent tunneling is expected and actually observed. (author)

  19. Proton tunneling in solids

    International Nuclear Information System (INIS)

    Kondo, J.

    1998-01-01

    The tunneling rate of the proton and its isotopes between interstitial sites in solids is studied theoretically. The phonons and/or the electrons in the solid have two effects on the tunneling phenomenon. First, they suppress the transfer integral between two neighbouring states. Second, they give rise to a finite lifetime of the proton state. Usually the second effect is large and the tunneling probability per unit time (tunneling rate) can be defined. In some cases, however, a coherent tunneling is expected and actually observed. (author)

  20. Reconstruction of large upper eyelid defects with a free tarsal plate graft and a myocutaneous pedicle flap plus a free skin graft

    DEFF Research Database (Denmark)

    Toft, Peter B

    2016-01-01

    skin graft. RESULTS: All patients healed without necrosis, did not suffer from lagophthalmos, achieved reasonable cosmesis, and did not need lubricants. In one patient, a contact lens was necessary for three weeks because of corneal erosion. One patient still needs a contact lens 3 months after...... excision to avoid eye discomfort. CONCLUSION: Large upper eyelid defects can be reconstructed with a free tarsal plate graft and a laterally based myocutaneous pedicle flap in combination with a free skin graft. Two-step procedures can probably be avoided in most cases....

  1. Quantum tunneling time

    International Nuclear Information System (INIS)

    Wang, Z.S.; Lai, C.H.; Oh, C.H.; Kwek, L.C.

    2004-01-01

    We present a calculation of quantum tunneling time based on the transition duration of wave peak from one side of a barrier to the other. In our formulation, the tunneling time comprises a real and an imaginary part. The real part is an extension of the phase tunneling time with quantum corrections whereas the imaginary time is associated with energy derivatives of the probability amplitudes

  2. Charge Islands Through Tunneling

    Science.gov (United States)

    Robinson, Daryl C.

    2002-01-01

    It has been recently reported that the electrical charge in a semiconductive carbon nanotube is not evenly distributed, but rather it is divided into charge "islands." This paper links the aforementioned phenomenon to tunneling and provides further insight into the higher rate of tunneling processes, which makes tunneling devices attractive. This paper also provides a basis for calculating the charge profile over the length of the tube so that nanoscale devices' conductive properties may be fully exploited.

  3. Josephson tunneling and nanosystems

    OpenAIRE

    Ovchinnikov, Yurii; Kresin, Vladimir

    2010-01-01

    Josephson tunneling between nanoclusters is analyzed. The discrete nature of the electronic energy spectra, including their shell ordering, is explicitly taken into account. The treatment considers the two distinct cases of resonant and non-resonant tunneling. It is demonstrated that the current density greatly exceeds the value discussed in the conventional theory. Nanoparticles are shown to be promising building blocks for nanomaterials-based tunneling networks.

  4. About tunnelling times

    International Nuclear Information System (INIS)

    Olkhovsky, V.S.; Recami, E.

    1991-08-01

    In this paper, first we critically analyse the main theoretical definitions and calculations of the sub-barrier tunnelling and reflection times. Secondly, we propose a new, physically sensible definition of such durations, on the basis of a recent general formalism (already tested for other types of quantum collisions). At last, we discuss some results regarding temporal evolution of the tunnelling processes, and in particular the ''particle'' speed during tunnelling. (author). 36 refs, 1 fig

  5. Microsystem Aeromechanics Wind Tunnel

    Data.gov (United States)

    Federal Laboratory Consortium — The Microsystem Aeromechanics Wind Tunnel advances the study of fundamental flow physics relevant to micro air vehicle (MAV) flight and assesses vehicle performance...

  6. Scanning tunneling microscopy

    International Nuclear Information System (INIS)

    Binnig, G.; Rohrer, H.

    1983-01-01

    Based on vacuum tunneling, a novel type of microscope, the scanning tunneling microscope (STM) was developed. It has an unprecedented resolution in real space on an atomic scale. The authors review the important technical features, illustrate the power of the STM for surface topographies and discuss its potential in other areas of science and technology. (Auth.)

  7. Electron tunneling in chemistry

    International Nuclear Information System (INIS)

    Zamaraev, K.I.; Khajrutdinov, R.F.; Zhdanov, V.P.; Molin, Yu.N.

    1985-01-01

    Results of experimental and theoretical investigations are outlined systematically on electron tunnelling in chemical reactions. Mechanism of electron transport to great distances is shown to be characteristic to chemical compounds of a wide range. The function of tunnel reactions is discussed for various fields of chemistry, including radiation chemistry, electrochemistry, chemistry of solids, chemistry of surface and catalysis

  8. Tunnel fire dynamics

    CERN Document Server

    Ingason, Haukur; Lönnermark, Anders

    2015-01-01

    This book covers a wide range of issues in fire safety engineering in tunnels, describes the phenomena related to tunnel fire dynamics, presents state-of-the-art research, and gives detailed solutions to these major issues. Examples for calculations are provided. The aim is to significantly improve the understanding of fire safety engineering in tunnels. Chapters on fuel and ventilation control, combustion products, gas temperatures, heat fluxes, smoke stratification, visibility, tenability, design fire curves, heat release, fire suppression and detection, CFD modeling, and scaling techniques all equip readers to create their own fire safety plans for tunnels. This book should be purchased by any engineer or public official with responsibility for tunnels. It would also be of interest to many fire protection engineers as an application of evolving technical principles of fire safety.

  9. Ultrafast scanning tunneling microscopy

    Energy Technology Data Exchange (ETDEWEB)

    Botkin, D.A. [California Univ., Berkeley, CA (United States). Dept. of Physics]|[Lawrence Berkeley Lab., CA (United States)

    1995-09-01

    I have developed an ultrafast scanning tunneling microscope (USTM) based on uniting stroboscopic methods of ultrafast optics and scanned probe microscopy to obtain nanometer spatial resolution and sub-picosecond temporal resolution. USTM increases the achievable time resolution of a STM by more than 6 orders of magnitude; this should enable exploration of mesoscopic and nanometer size systems on time scales corresponding to the period or decay of fundamental excitations. USTM consists of a photoconductive switch with subpicosecond response time in series with the tip of a STM. An optical pulse from a modelocked laser activates the switch to create a gate for the tunneling current, while a second laser pulse on the sample initiates a dynamic process which affects the tunneling current. By sending a large sequence of identical pulse pairs and measuring the average tunnel current as a function of the relative time delay between the pulses in each pair, one can map the time evolution of the surface process. USTM was used to measure the broadband response of the STM`s atomic size tunnel barrier in frequencies from tens to hundreds of GHz. The USTM signal amplitude decays linearly with the tunnel junction conductance, so the spatial resolution of the time-resolved signal is comparable to that of a conventional STM. Geometrical capacitance of the junction does not appear to play an important role in the measurement, but a capacitive effect intimately related to tunneling contributes to the measured signals and may limit the ultimate resolution of the USTM.

  10. Reconstruction of the Midfoot Using a Free Vascularized Fibular Graft After En Bloc Excision for Giant Cell Tumor of the Tarsal Bones: A Case Report.

    Science.gov (United States)

    Hara, Hitomi; Kawamoto, Teruya; Onishi, Yasuo; Fujioka, Hiroyuki; Nishida, Kotaro; Kuroda, Ryosuke; Kurosaka, Masahiro; Akisue, Toshihiro

    2016-01-01

    We report the case of a 32-year-old Japanese female with a giant cell tumor of bone involving multiple midfoot bones. Giant cell tumors of bone account for approximately 5% of all primary bone tumors and most often arise at the ends of long bones. The small bones, such as those of the hands and feet, are rare sites for giant cell tumors. Giant cell tumors of the small bones tend to exhibit more aggressive clinical behavior than those of the long bones. The present patient underwent en bloc tumor excision involving multiple tarsals and metatarsals. We reconstructed the longitudinal arch of the foot with a free vascularized fibular graft. At the 2-year follow-up visit, bony union had been achieved, with no tumor recurrence. Copyright © 2016 American College of Foot and Ankle Surgeons. Published by Elsevier Inc. All rights reserved.

  11. Tunnel magnetoresistance in alumina, magnesia and composite tunnel barrier magnetic tunnel junctions

    International Nuclear Information System (INIS)

    Schebaum, Oliver; Drewello, Volker; Auge, Alexander; Reiss, Guenter; Muenzenberg, Markus; Schuhmann, Henning; Seibt, Michael; Thomas, Andy

    2011-01-01

    Using magnetron sputtering, we have prepared Co-Fe-B/tunnel barrier/Co-Fe-B magnetic tunnel junctions with tunnel barriers consisting of alumina, magnesia, and magnesia-alumina bilayer systems. The highest tunnel magnetoresistance ratios we found were 73% for alumina and 323% for magnesia-based tunnel junctions. Additionally, tunnel junctions with a unified layer stack were prepared for the three different barriers. In these systems, the tunnel magnetoresistance ratios at optimum annealing temperatures were found to be 65% for alumina, 173% for magnesia, and 78% for the composite tunnel barriers. The similar tunnel magnetoresistance ratios of the tunnel junctions containing alumina provide evidence that coherent tunneling is suppressed by the alumina layer in the composite tunnel barrier. - Research highlights: → Transport properties of Co-Fe-B/tunnel barrier/Co-Fe-B magnetic tunnel junctions. → Tunnel barrier consists of MgO, Al-Ox, or MgO/Al-Ox bilayer systems. → Limitation of TMR-ratio in composite barrier tunnel junctions to Al-Ox values. → Limitation indicates that Al-Ox layer is causing incoherent tunneling.

  12. Tunneling current between graphene layers

    OpenAIRE

    Poklonski, Nikolai A.; Siahlo, Andrei I.; Vyrko, Sergey A.; Popov, Andrey M.; Lozovik, Yurii E.

    2013-01-01

    The physical model that allows to calculate the values of the tunneling current be-tween graphene layers is proposed. The tunneling current according to the pro-posed model is proportional to the area of tunneling transition. The calculated value of tunneling conductivity is in qualitative agreement with experimental data.

  13. Vacuum phonon tunneling.

    Science.gov (United States)

    Altfeder, Igor; Voevodin, Andrey A; Roy, Ajit K

    2010-10-15

    Field-induced phonon tunneling, a previously unknown mechanism of interfacial thermal transport, has been revealed by ultrahigh vacuum inelastic scanning tunneling microscopy (STM). Using thermally broadened Fermi-Dirac distribution in the STM tip as in situ atomic-scale thermometer we found that thermal vibrations of the last tip atom are effectively transmitted to sample surface despite few angstroms wide vacuum gap. We show that phonon tunneling is driven by interfacial electric field and thermally vibrating image charges, and its rate is enhanced by surface electron-phonon interaction.

  14. Quantum tunneling with friction

    Science.gov (United States)

    Tokieda, M.; Hagino, K.

    2017-05-01

    Using the phenomenological quantum friction models introduced by P. Caldirola [Nuovo Cimento 18, 393 (1941), 10.1007/BF02960144] and E. Kanai [Prog. Theor. Phys. 3, 440 (1948), 10.1143/ptp/3.4.440], M. D. Kostin [J. Chem. Phys. 57, 3589 (1972), 10.1063/1.1678812], and K. Albrecht [Phys. Lett. B 56, 127 (1975), 10.1016/0370-2693(75)90283-X], we study quantum tunneling of a one-dimensional potential in the presence of energy dissipation. To this end, we calculate the tunneling probability using a time-dependent wave-packet method. The friction reduces the tunneling probability. We show that the three models provide similar penetrabilities to each other, among which the Caldirola-Kanai model requires the least numerical effort. We also discuss the effect of energy dissipation on quantum tunneling in terms of barrier distributions.

  15. Wind Tunnel Testing Facilities

    Data.gov (United States)

    Federal Laboratory Consortium — NASA Ames Research Center is pleased to offer the services of our premier wind tunnel facilities that have a broad range of proven testing capabilities to customers...

  16. INCAS TRISONIC WIND TUNNEL

    Directory of Open Access Journals (Sweden)

    Florin MUNTEANU

    2009-09-01

    Full Text Available The 1.2 m x 1.2 m Trisonic Blowdown Wind Tunnel is the largest of the experimental facilities at the National Institute for Aerospace Research - I.N.C.A.S. "Elie Carafoli", Bucharest, Romania. The tunnel has been designed by the Canadian company DSMA (now AIOLOS and since its commissioning in 1978 has performed high speed aerodynamic tests for more than 120 projects of aircraft, missiles and other objects among which the twin jet fighter IAR-93, the jet trainer IAR-99, the MIG-21 Lancer, the Polish jet fighter YRYDA and others. In the last years the wind tunnel has been used mostly for experimental research in European projects such as UFAST. The high flow quality parameters and the wide range of testing capabilities ensure the competitivity of the tunnel at an international level.

  17. The ISI Tunnel

    Science.gov (United States)

    1993-10-01

    DP /etc/tunnelvisa p zephyr dark -star TCP /etc/tunnelvisa p zephyr dak’star ICMP /etc/tunnelvisa p zephyr quark MDP /etc/tunnelvisa p zephyr quark ...drax-net-yp 128.9.32.2 1 route add quark -net-yp 128.9.32.3 1 route add vlsi-net-yp 128.9.32.4 1 route add darkstar-net-yp 128.9.32.3 1 route add rocky...TCP /etc/tunnel-visa p zephyr quark ICMP /etc/tunnel-visa p zephyr drax tTI)P /etc/tunnel-visa p zephyr drax TCP /etc/tunnel_visa p zephyr drax ICMP

  18. Wind Tunnel Facility

    Data.gov (United States)

    Federal Laboratory Consortium — This ARDEC facility consists of subsonic, transonic, and supersonic wind tunnels to acquire aerodynamic data. Full-scale and sub-scale models of munitions are fitted...

  19. Water Tunnel Facility

    Data.gov (United States)

    Federal Laboratory Consortium — NETL’s High-Pressure Water Tunnel Facility in Pittsburgh, PA, re-creates the conditions found 3,000 meters beneath the ocean’s surface, allowing scientists to study...

  20. The Beginner's Guide to Wind Tunnels with TunnelSim and TunnelSys

    Science.gov (United States)

    Benson, Thomas J.; Galica, Carol A.; Vila, Anthony J.

    2010-01-01

    The Beginner's Guide to Wind Tunnels is a Web-based, on-line textbook that explains and demonstrates the history, physics, and mathematics involved with wind tunnels and wind tunnel testing. The Web site contains several interactive computer programs to demonstrate scientific principles. TunnelSim is an interactive, educational computer program that demonstrates basic wind tunnel design and operation. TunnelSim is a Java (Sun Microsystems Inc.) applet that solves the continuity and Bernoulli equations to determine the velocity and pressure throughout a tunnel design. TunnelSys is a group of Java applications that mimic wind tunnel testing techniques. Using TunnelSys, a team of students designs, tests, and post-processes the data for a virtual, low speed, and aircraft wing.

  1. Tunnelling of a molecule

    International Nuclear Information System (INIS)

    Jarvis, P.D.; Bulte, D.P.

    1998-01-01

    A quantum-mechanical description of tunnelling is presented for a one-dimensional system with internal oscillator degrees of freedom. The 'charged diatomic molecule' is frustrated on encountering a barrier potential by its centre of charge not being coincident with its centre of mass, resulting in transitions amongst internal states. In an adiabatic limit, the tunnelling of semiclassical coherent-like oscillator states is shown to exhibit the Hartman and Bueuttiker-Landauer times t H and t BL , with the time dependence of the coherent state parameter for the tunnelled state given by α(t) = α e -iω(t+Δt) , Δt = t H - it BL . A perturbation formalism is developed, whereby the exact transfer matrix can be expanded to any desired accuracy in a suitable limit. An 'intrinsic' time, based on the oscillator transition rate during tunnelling, transmission or reflection, is introduced. In simple situations the resulting intrinsic tunnelling time is shown to vanish to lowest order. In the general case a particular (nonzero) parametrisation is inferred, and its properties discussed in comparison with the literature on tunnelling times for both wavepackets and internal clocks. Copyright (1998) CSIRO Australia

  2. Single Electron Tunneling

    International Nuclear Information System (INIS)

    Ruggiero, Steven T.

    2005-01-01

    Financial support for this project has led to advances in the science of single-electron phenomena. Our group reported the first observation of the so-called ''Coulomb Staircase'', which was produced by tunneling into ultra-small metal particles. This work showed well-defined tunneling voltage steps of width e/C and height e/RC, demonstrating tunneling quantized on the single-electron level. This work was published in a now well-cited Physical Review Letter. Single-electron physics is now a major sub-field of condensed-matter physics, and fundamental work in the area continues to be conducted by tunneling in ultra-small metal particles. In addition, there are now single-electron transistors that add a controlling gate to modulate the charge on ultra-small photolithographically defined capacitive elements. Single-electron transistors are now at the heart of at least one experimental quantum-computer element, and single-electron transistor pumps may soon be used to define fundamental quantities such as the farad (capacitance) and the ampere (current). Novel computer technology based on single-electron quantum dots is also being developed. In related work, our group played the leading role in the explanation of experimental results observed during the initial phases of tunneling experiments with the high-temperature superconductors. When so-called ''multiple-gap'' tunneling was reported, the phenomenon was correctly identified by our group as single-electron tunneling in small grains in the material. The main focus throughout this project has been to explore single electron phenomena both in traditional tunneling formats of the type metal/insulator/particles/insulator/metal and using scanning tunneling microscopy to probe few-particle systems. This has been done under varying conditions of temperature, applied magnetic field, and with different materials systems. These have included metals, semi-metals, and superconductors. Amongst a number of results, we have

  3. Resonant tunnel magnetoresistance in a double magnetic tunnel junction

    KAUST Repository

    Useinov, Arthur; Useinov, Niazbeck Kh H; Tagirov, Lenar R.; Kosel, Jü rgen

    2011-01-01

    We present quasi-classical approach to calculate a spin-dependent current and tunnel magnetoresistance (TMR) in double magnetic tunnel junctions (DMTJ) FML/I/FMW/I/FMR, where the magnetization of the middle ferromagnetic metal layer FMW can

  4. Interaction between groundwater and TBM (Tunnel Boring Machine) excavated tunnels

    OpenAIRE

    Font Capó, Jordi

    2012-01-01

    A number of problems, e.g. sudden inflows are encountered during tunneling under the piezometric level, especially when the excavation crosses high transmissivity areas. These inflows may drag materials when the tunnel crosses low competent layers, resulting in subsidence, chimney formation and collapses. Moreover, inflows can lead to a decrease in head level because of aquifer drainage. Tunnels can be drilled by a tunnel boring machine (TBM) to minimize inflows and groundwater impacts, restr...

  5. Seepage into PEP tunnel

    International Nuclear Information System (INIS)

    Weidner, H.

    1990-01-01

    The current rate of seepage into the PEP tunnel in the vicinity of IR-10 is very low compared to previous years. Adequate means of handling this low flow are in place. It is not clear whether the reduction in the flow is temporary, perhaps due to three consecutive dry years, or permanent due to drainage of a perched water table. During PEP construction a large amount of effort was expended in attempts to seal the tunnel, with no immediate effect. The efforts to ''manage'' the water flow are deemed to be successful. By covering equipment to protect it from dripping water and channeling seepage into the drainage gutters, the seepage has been reduced to a tolerable nuisance. There is no sure, safe procedure for sealing a leaky shotcreted tunnel

  6. Uncooled tunneling infrared sensor

    Science.gov (United States)

    Kenny, Thomas W. (Inventor); Kaiser, William J. (Inventor); Podosek, Judith A. (Inventor); Vote, Erika C. (Inventor); Muller, Richard E. (Inventor); Maker, Paul D. (Inventor)

    1995-01-01

    An uncooled infrared tunneling sensor in which the only moving part is a diaphragm which is deflected into contact with a micromachined silicon tip electrode prepared by a novel lithographic process. Similarly prepared deflection electrodes employ electrostatic force to control the deflection of a silicon nitride, flat diaphragm membrane. The diaphragm exhibits a high resonant frequency which reduces the sensor's sensitivity to vibration. A high bandwidth feedback circuit controls the tunneling current by adjusting the deflection voltage to maintain a constant deflection of the membrane. The resulting infrared sensor can be miniaturized to pixel dimensions smaller than 100 .mu.m. An alternative embodiment is implemented using a corrugated membrane to permit large deflection without complicated clamping and high deflection voltages. The alternative embodiment also employs a pinhole aperture in a membrane to accommodate environmental temperature variation and a sealed chamber to eliminate environmental contamination of the tunneling electrodes and undesireable accoustic coupling to the sensor.

  7. Instabilities in thin tunnel junctions

    International Nuclear Information System (INIS)

    Konkin, M.K.; Adler, J.G.

    1978-01-01

    Tunnel junctions prepared for inelastic electron tunneling spectroscopy are often plagued by instabilities in the 0-500-meV range. This paper relates the bias at which the instability occurs to the barrier thickness

  8. Tunneling in axion monodromy

    Energy Technology Data Exchange (ETDEWEB)

    Brown, Jon; Cottrell, William; Shiu, Gary; Soler, Pablo [Department of Physics, University of Wisconsin,Madison, WI 53706 (United States)

    2016-10-06

    The Coleman formula for vacuum decay and bubble nucleation has been used to estimate the tunneling rate in models of axion monodromy in recent literature. However, several of Coleman’s original assumptions do not hold for such models. Here we derive a new estimate with this in mind using a similar Euclidean procedure. We find that there are significant regions of parameter space for which the tunneling rate in axion monodromy is not well approximated by the Coleman formula. However, there is also a regime relevant to large field inflation in which both estimates parametrically agree. We also briefly comment on the applications of our results to the relaxion scenario.

  9. LEP tunnel monorail

    CERN Multimedia

    1985-01-01

    A monorail from CERN's Large Electron Positron collider (LEP, for short). It ran around the 27km tunnel, transporting equipment and personnel. With its 27-kilometre circumference, LEP was the largest electron-positron accelerator ever built and ran from 1989 to 2000. During 11 years of research, LEP's experiments provided a detailed study of the electroweak interaction. Measurements performed at LEP also proved that there are three – and only three – generations of particles of matter. LEP was closed down on 2 November 2000 to make way for the construction of the Large Hadron Collider in the same tunnel.

  10. Excavating a transfer tunnel

    CERN Multimedia

    Laurent Guiraud

    2000-01-01

    The transfer tunnel being dug here will take the 450 GeV beam from the SPS and inject it into the LHC where the beam energies will be increased to 7 TeV. In order to transfer this beam from the SPS to the LHC, two transfer tunnels are used to circulate the beams in opposite directions. When excavated, the accelerator components, including magnets, beam pipes and cryogenics will be installed and connected to both the SPS and LHC ready for operation to begin in 2008.

  11. Gap anisotropy and tunneling currents. [MPS3

    DEFF Research Database (Denmark)

    Lazarides, N.; Sørensen, Mads Peter

    1996-01-01

    The tunneling Hamiltonian formalism is applied to calculate the tunnelingcurrents through a small superconducting tunnel junction. The formalism isextended to nonconstant tunneling matrix elements. The electrodes of thejunction are assumed to......The tunneling Hamiltonian formalism is applied to calculate the tunnelingcurrents through a small superconducting tunnel junction. The formalism isextended to nonconstant tunneling matrix elements. The electrodes of thejunction are assumed to...

  12. Breaking through the tranfer tunnel

    CERN Document Server

    Laurent Guiraud

    2001-01-01

    This image shows the tunnel boring machine breaking through the transfer tunnel into the LHC tunnel. Proton beams will be transferred from the SPS pre-accelerator to the LHC at 450 GeV through two specially constructed transfer tunnels. From left to right: LHC Project Director, Lyn Evans; CERN Director-General (at the time), Luciano Maiani, and Director for Accelerators, Kurt Hubner.

  13. Control of tunneling in heterostructures

    International Nuclear Information System (INIS)

    Volokhov, V M; Tovstun, C A; Ivlev, B

    2007-01-01

    A tunneling current between two rectangular potential wells can be effectively controlled by applying an external ac field. A variation of the ac frequency by 10% may lead to the suppression of the tunneling current by two orders of magnitude, which is a result of quantum interference under the action of the ac field. This effect of destruction of tunneling can be used as a sensitive control of tunneling current across nanosize heterostructures

  14. Ivar Giaever, Tunneling, and Superconductors

    Science.gov (United States)

    dropdown arrow Site Map A-Z Index Menu Synopsis Ivar Giaever, Tunneling, and Superconductors Resources with in Superconductors Measured by Electron Tunneling; Physical Review Letters, Vol. 5 Issue 4: 147 - 148 ; August 15, 1960 Electron Tunneling Between Two Superconductors; Physical Review Letters, Vol. 5 Issue 10

  15. Scanning tunneling microscope nanoetching method

    Science.gov (United States)

    Li, Yun-Zhong; Reifenberger, Ronald G.; Andres, Ronald P.

    1990-01-01

    A method is described for forming uniform nanometer sized depressions on the surface of a conducting substrate. A tunneling tip is used to apply tunneling current density sufficient to vaporize a localized area of the substrate surface. The resulting depressions or craters in the substrate surface can be formed in information encoding patterns readable with a scanning tunneling microscope.

  16. Physics of optimal resonant tunneling

    NARCIS (Netherlands)

    Racec, P.N.; Stoica, T.; Popescu, C.; Lepsa, M.I.; Roer, van de T.G.

    1997-01-01

    The optimal resonant tunneling, or the complete tunneling transparence of a biased double-barrier resonant-tunneling (DBRT) structure, is discussed. It is shown that its physics does not rest on the departure from the constant potential within the barriers and well, due to the applied electric

  17. Acoustic emission and ultrasonic-velocity methods used to characterise the excavation disturbance associated with deep tunnels in hard rock

    Science.gov (United States)

    Falls, Stephen D.; Young, R. Paul

    1998-04-01

    Acoustic emission (AE) and ultrasonic-velocity monitoring studies have been undertaken at both the Atomic Energy of Canada Limited (AECL) Underground Research Laboratory (URL) and at the Swedish Nuclear Fuel Waste Management Company (SKB) Hard Rock Laboratory (HRL). At both locations the excavations were tunnels in granitic material at approximately 420 m depth. However, the stress regime was more severe at the URL Mine-by tunnel site than the HRL ZEDEX tunnel. Different parts of the ZEDEX tunnel were created using different excavation techniques. Using AE and ultrasonic techniques to study these tunnels we have been able to examine the nature of the excavation-disturbed zone around the tunnel, as well as examining the effects of different stress regimes and excavation techniques. Studies were undertaken both during and after the Mine-by tunnel excavation and during excavation in the ZEDEX tunnel. AE monitoring in the wall of the Mine-by tunnel during excavation showed that some activity occurred in the sidewall regions, but the spatial density of AE hypocentres increased toward the regions in the floor and roof of the tunnel where breakout notches formed. This sidewall activity was clustered primarily within 0.5 m of the tunnel wall. AE monitoring in the floor of the tunnel showed that small numbers of AE continued to occur in the notch region in the floor of the tunnel over 2 years after excavation was completed. This activity became more acute as the rock was heated, imposing thermally induced stresses on the volume. Ultrasonic-velocity studies both in the floor and the wall of the tunnel showed that the velocity is strongly anisotropic with the direction of slowest velocity orthogonal to the tunnel surface. The velocity increased with distance into the rock from the tunnel surface. In the floor, this effect was seen up to 2 m from the tunnel surface. Most of the change occurred within the first 0.5 m from the tunnel perimeter. At the lower-stress HRL, most of

  18. Tunneling path toward spintronics

    International Nuclear Information System (INIS)

    Miao Guoxing; Moodera, Jagadeesh S; Muenzenberg, Markus

    2011-01-01

    The phenomenon of quantum tunneling, which was discovered almost a century ago, has led to many subsequent discoveries. One such discovery, spin polarized tunneling, was made 40 years ago by Robert Meservey and Paul Tedrow (Tedrow and Meservey 1971 Phys. Rev. Lett. 26 192), and it has resulted in many fundamental observations and opened up an entirely new field of study. Until the mid-1990s, this field developed at a steady, low rate, after which a huge increase in activity suddenly occurred as a result of the unraveling of successful spin tunneling between two ferromagnets. In the past 15 years, several thousands of papers related to spin polarized tunneling and transport have been published, making this topic one of the hottest areas in condensed matter physics from both fundamental science and applications viewpoints. Many review papers and book chapters have been written in the past decade on this subject. This paper is not exhaustive by any means; rather, the emphases are on recent progress, technological developments and informing the reader about the current direction in which this topic is moving.

  19. Magnetic Fluxtube Tunneling

    Science.gov (United States)

    Dahlburg, Russell B.; Antiochos,, Spiro K.; Norton, D.

    1996-01-01

    We present numerical simulations of the collision and subsequent interaction of two initially orthogonal, twisted, force free field magnetic fluxtubes. The simulations were carried out using a new three dimensional explicit parallelized Fourier collocation algorithm for solving the viscoresistive equations of compressible magnetohydrodynamics. It is found that, under a wide range of conditions, the fluxtubes can 'tunnel' through each other. Two key conditions must be satisfied for tunneling to occur: the magnetic field must be highly twisted with a field line pitch much greater than 1, and the magnetic Lundquist number must be somewhat large, greater than or equal to 2880. This tunneling behavior has not been seen previously in studies of either vortex tube or magnetic fluxtube interactions. An examination of magnetic field lines shows that tunneling is due to a double reconnection mechanism. Initially orthogonal field lines reconnect at two specific locations, exchange interacting sections and 'pass' through each other. The implications of these results for solar and space plasmas are discussed.

  20. Tunnel nitrogen spill experiment

    International Nuclear Information System (INIS)

    Ageyev, A.I.; Alferov, V.N.; Mulholland, G.T.

    1983-01-01

    The Energy Saver Safety Analysis Report (SAR) found the tunnel oxygen deficiency considerations emphasized helium spills. These reports concluded the helium quickly warms and because of its low denisty, rises to the apex of the tunnel. The oxygen content below the apex and in all but the immediate vicinity of the helium spill is essentially unchanged and guarantees an undisturbed source of oxygen especially important to fallen personnel. In contrast nitrogen spills warm slower than helium due to the ratio of the enthalpy changes per unit volume spilled spread more uniformly across the tunnel cross-section when warmed because of the much smaller density difference with air, and generally provides a greater hazard than helium spills as a result. In particular there was concern that personnel that might fall to the floor for oxygen deficiency or other reasons might find less, and not more, oxygen with dire consequences. The SAR concluded tunnel nitrogen spills were under-investigated and led to this work

  1. The scanning tunneling microscope

    International Nuclear Information System (INIS)

    Salvan, F.

    1986-01-01

    A newly conceived microscope, based on a pure quantum phenomenon, is an ideal tool to study atom by atom the topography and properties of surfaces. Applications are presented: surface ''reconstruction'' of silicon, lamellar compound study, etc... Spectroscopy by tunnel effect will bring important information on electronic properties; it is presented with an application on silicon [fr

  2. Supramolecular tunneling junctions

    NARCIS (Netherlands)

    Wimbush, K.S.

    2012-01-01

    In this study a variety of supramolecular tunneling junctions were created. The basis of these junctions was a self-assembled monolayer of heptathioether functionalized ß-cyclodextrin (ßCD) formed on an ultra-flat Au surface, i.e., the bottom electrode. This gave a well-defined hexagonally packed

  3. Monitoring pilot projects on bored tunnelling : The Second Heinenoord Tunnel and the Botlek Rail Tunnel

    NARCIS (Netherlands)

    Bakker, K.J.; De Boer, F.; Admiraal, J.B.M.; Van Jaarsveld, E.P.

    1999-01-01

    Two pilot projects for bored tunnelling in soft soil have been undertaken in the Netherlands. The monitoring was commissioned under the authority of the Centre for Underground Construction (COB). A description of the research related to the Second Heinenoord Tunnel and the Botlek Rail Tunnel will be

  4. Measuring fire size in tunnels

    International Nuclear Information System (INIS)

    Guo, Xiaoping; Zhang, Qihui

    2013-01-01

    A new measure of fire size Q′ has been introduced in longitudinally ventilated tunnel as the ratio of flame height to the height of tunnel. The analysis in this article has shown that Q′ controls both the critical velocity and the maximum ceiling temperature in the tunnel. Before the fire flame reaches tunnel ceiling (Q′ 1.0), Fr approaches a constant value. This is also a well-known phenomenon in large tunnel fires. Tunnel ceiling temperature shows the opposite trend. Before the fire flame reaches the ceiling, it increases very slowly with the fire size. Once the flame has hit the ceiling of tunnel, temperature rises rapidly with Q′. The good agreement between the current prediction and three different sets of experimental data has demonstrated that the theory has correctly modelled the relation among the heat release rate of fire, ventilation flow and the height of tunnel. From design point of view, the theoretical maximum of critical velocity for a given tunnel can help to prevent oversized ventilation system. -- Highlights: • Fire sizing is an important safety measure in tunnel design. • New measure of fire size a function of HRR of fire, tunnel height and ventilation. • The measure can identify large and small fires. • The characteristics of different fire are consistent with observation in real fires

  5. Tunnel boring machine applications

    International Nuclear Information System (INIS)

    Bhattacharyya, K.K.; McDonald, R.; Saunders, R.S.

    1992-01-01

    This paper reports that characterization of Yucca Mountain for a potential repository requires construction of an underground Exploratory Studies Facility (ESF). Mechanical excavating methods have been proposed for construction of the ESF as they offer a number of advantages over drilling and blasting at the Yucca Mountain site, including; less ground disturbance and therefore a potential for less adverse effects on the integrity of the site, creation of a more stable excavation cross section requiring less ground support, and an inherently safer and cleaner working environment. The tunnel boring machine (TBM) provides a proven technology for excavating the welded and unwelded Yucca Mountain tuffs. The access ramps and main underground tunnels form the largest part of the ESF underground construction work, and have been designed for excavation by TBM

  6. Programmable ferroelectric tunnel memristor

    Directory of Open Access Journals (Sweden)

    Andy eQuindeau

    2014-02-01

    Full Text Available We report an analogously programmable memristor based on genuine electronic resistive switching combining ferroelectric switching and electron tunneling. The tunnel current through an 8 unit cell thick epitaxial Pb(Zr[0.2]Ti[0.8]O[3] film sandwiched between La[0.7]Sr[0.3]MnO[3] and cobalt electrodes obeys the Kolmogorov-Avrami-Ishibashi model for bidimensional growth with a characteristic switching time in the order of 10^-7 seconds. The analytical description of switching kinetics allows us to develop a characteristic transfer function that has only one parameter viz. the characteristic switching time and fully predicts the resistive states of this type of memristor.

  7. Hawking Radiation As Tunneling

    International Nuclear Information System (INIS)

    Parikh, Maulik K.; Wilczek, Frank

    2000-01-01

    We present a short and direct derivation of Hawking radiation as a tunneling process, based on particles in a dynamical geometry. The imaginary part of the action for the classically forbidden process is related to the Boltzmann factor for emission at the Hawking temperature. Because the derivation respects conservation laws, the exact spectrum is not precisely thermal. We compare and contrast the problem of spontaneous emission of charged particles from a charged conductor

  8. Tunnel blasting - recent developments

    Energy Technology Data Exchange (ETDEWEB)

    White, T.E.

    1999-05-01

    While tunnelling machines are more efficient than previously, there are still areas where blasting is a more efficient method of advance. Drilling and design methods are increasingly sophisticated, as is choice of explosive. Explosive deployment must be carefully calculated so as to avoid desensitisation. Nitroglycerine may be used as slurries; bulk mixing on site of ANFO is also practised in mining in the UK. Electric detonators, Nonel tubes, and electronic detonators are also increasingly employed.

  9. The beam dump tunnels

    CERN Multimedia

    Patrice Loïez

    2002-01-01

    In these images workers are digging the tunnels that will be used to dump the counter-circulating beams. Travelling just a fraction under the speed of light, the beams at the LHC will each carry the energy of an aircraft carrier travelling at 12 knots. In order to dispose of these beams safely, a beam dump is used to extract the beam and diffuse it before it collides with a radiation shielded graphite target.

  10. Primary Tunnel Junction Thermometry

    International Nuclear Information System (INIS)

    Pekola, Jukka P.; Holmqvist, Tommy; Meschke, Matthias

    2008-01-01

    We describe the concept and experimental demonstration of primary thermometry based on a four-probe measurement of a single tunnel junction embedded within four arrays of junctions. We show that in this configuration random sample specific and environment-related errors can be avoided. This method relates temperature directly to Boltzmann constant, which will form the basis of the definition of temperature and realization of official temperature scales in the future

  11. Hydrodynamic optical soliton tunneling

    Science.gov (United States)

    Sprenger, P.; Hoefer, M. A.; El, G. A.

    2018-03-01

    A notion of hydrodynamic optical soliton tunneling is introduced in which a dark soliton is incident upon an evolving, broad potential barrier that arises from an appropriate variation of the input signal. The barriers considered include smooth rarefaction waves and highly oscillatory dispersive shock waves. Both the soliton and the barrier satisfy the same one-dimensional defocusing nonlinear Schrödinger (NLS) equation, which admits a convenient dispersive hydrodynamic interpretation. Under the scale separation assumption of nonlinear wave (Whitham) modulation theory, the highly nontrivial nonlinear interaction between the soliton and the evolving hydrodynamic barrier is described in terms of self-similar, simple wave solutions to an asymptotic reduction of the Whitham-NLS partial differential equations. One of the Riemann invariants of the reduced modulation system determines the characteristics of a soliton interacting with a mean flow that results in soliton tunneling or trapping. Another Riemann invariant yields the tunneled soliton's phase shift due to hydrodynamic interaction. Soliton interaction with hydrodynamic barriers gives rise to effects that include reversal of the soliton propagation direction and spontaneous soliton cavitation, which further suggest possible methods of dark soliton control in optical fibers.

  12. Resonant Tunneling Spin Pump

    Science.gov (United States)

    Ting, David Z.

    2007-01-01

    The resonant tunneling spin pump is a proposed semiconductor device that would generate spin-polarized electron currents. The resonant tunneling spin pump would be a purely electrical device in the sense that it would not contain any magnetic material and would not rely on an applied magnetic field. Also, unlike prior sources of spin-polarized electron currents, the proposed device would not depend on a source of circularly polarized light. The proposed semiconductor electron-spin filters would exploit the Rashba effect, which can induce energy splitting in what would otherwise be degenerate quantum states, caused by a spin-orbit interaction in conjunction with a structural-inversion asymmetry in the presence of interfacial electric fields in a semiconductor heterostructure. The magnitude of the energy split is proportional to the electron wave number. Theoretical studies have suggested the possibility of devices in which electron energy states would be split by the Rashba effect and spin-polarized currents would be extracted by resonant quantum-mechanical tunneling.

  13. Submucosal tunneling techniques: current perspectives.

    Science.gov (United States)

    Kobara, Hideki; Mori, Hirohito; Rafiq, Kazi; Fujihara, Shintaro; Nishiyama, Noriko; Ayaki, Maki; Yachida, Tatsuo; Matsunaga, Tae; Tani, Johji; Miyoshi, Hisaaki; Yoneyama, Hirohito; Morishita, Asahiro; Oryu, Makoto; Iwama, Hisakazu; Masaki, Tsutomu

    2014-01-01

    Advances in endoscopic submucosal dissection include a submucosal tunneling technique, involving the introduction of tunnels into the submucosa. These tunnels permit safer offset entry into the peritoneal cavity for natural orifice transluminal endoscopic surgery. Technical advantages include the visual identification of the layers of the gut, blood vessels, and subepithelial tumors. The creation of a mucosal flap that minimizes air and fluid leakage into the extraluminal cavity can enhance the safety and efficacy of surgery. This submucosal tunneling technique was adapted for esophageal myotomy, culminating in its application to patients with achalasia. This method, known as per oral endoscopic myotomy, has opened up the new discipline of submucosal endoscopic surgery. Other clinical applications of the submucosal tunneling technique include its use in the removal of gastrointestinal subepithelial tumors and endomicroscopy for the diagnosis of functional and motility disorders. This review suggests that the submucosal tunneling technique, involving a mucosal safety flap, can have potential values for future endoscopic developments.

  14. Comparison of Polypropylene Sling with Combined Transconjunctival Retractor Plication and Lateral Tarsal Strip for Correction of Involutional Lower Eye Lid Ectropion.

    Science.gov (United States)

    Goel, Ruchi; Sanoria, Abhilasha; Kumar, Sushil; Arya, Deepanjali; Nagpal, Smriti; Rathie, Neha

    2017-01-01

    The study aims to compare the effectiveness and complications of transconjunctival retractor plication (TRP) with lateral tarsal strip (LTS) and the polypropylene sling (PS) surgery for treatment of involutional lower lid ectropion. A prospective randomised pilot study was conducted on 30 eyes of 30 patients suffering from epiphora having horizontal eyelid laxity >6mm and age >50 years at a tertiary care centre from December 2014 to March 2015. They were randomly divided into two equal groups for TRP with LTS (group A) and PS (group B). Success was defined as relief in epiphora and lid laxity ≤4mm at 12 months post operatively. There were 19 male and 11 female patients with age ranging from 55-80 years. The mean grade of ectropion was 2.80±1.32 in group A and 2.87±1.60 in group B. The preoperative horizontal laxity increased with the grade of ectropion (p <0.001) while medial canthal laxity was variable. The average surgical time per procedure in group A was 66 minutes and in group B was 24 minutes. Group A had a success rate of 93.33%, while group B had a success rate of 87%. Post-operative complications occurred in 2 eyes in group B only. Both LTS with TRP and PS are effective in the management of involutional ectropion. LTS with TRP though more invasive has higher success rates and a lower incidence of complications as compared to PS. However, PS is an easy to perform out- patient procedure that is faster and better tolerated in old patients.

  15. Semiclassical description of resonant tunneling

    International Nuclear Information System (INIS)

    Bogomolny, E.B.; Rouben, D.C.

    1996-01-01

    A semiclassical formula is calculated for the tunneling current of electrons trapped in a potential well which can tunnel into and across a wide quantum well. The tunneling current is measured at the second interface of this well and the calculations idealized an experimental situation where a strong magnetic field tilted with respect to an electric field was used. It is shown that the contribution to the tunneling current, due to trajectories which begin at the first interface and end on the second, is dominant for periodic orbits which hit both walls of the quantum well. (author)

  16. Engineers win award for Swiss tunnel

    CERN Multimedia

    2003-01-01

    A Derby engineering consultancy has won the Tunnelling Industry Award 2003 for Excellence in Tunnel Design, offered by the British Tunnelling Society, for its work on the LHC in Geneva, Switzerland (1/2 page).

  17. Thermovoltages in vacuum tunneling investigated by scanning tunneling microscopy

    OpenAIRE

    Hoffmann, D. H.; Rettenberger, Armin; Grand, Jean Yves; Läuger, K.; Leiderer, Paul; Dransfeld, Klaus; Möller, Rolf

    1995-01-01

    By heating the tunneling tip of a scanning tunneling microscope the thermoelectric properties of a variable vacuum barrier have been investigated. The lateral variation of the observed thermovoltage will be discussed for polycrystalline gold, stepped surfaces of silver, as well as for copper islands on silver.

  18. Magnetic tunnel junctions with monolayer hexagonal boron nitride tunnel barriers

    Energy Technology Data Exchange (ETDEWEB)

    Piquemal-Banci, M.; Galceran, R.; Bouzehouane, K.; Anane, A.; Petroff, F.; Fert, A.; Dlubak, B.; Seneor, P. [Unité Mixte de Physique, CNRS, Thales, Univ. Paris-Sud, Université Paris-Saclay, Palaiseau 91767 (France); Caneva, S.; Martin, M.-B.; Weatherup, R. S.; Kidambi, P. R.; Robertson, J.; Hofmann, S. [Department of Engineering, University of Cambridge, Cambridge CB21PZ (United Kingdom); Xavier, S. [Thales Research and Technology, 1 avenue Augustin Fresnel, Palaiseau 91767 (France)

    2016-03-07

    We report on the integration of atomically thin 2D insulating hexagonal boron nitride (h-BN) tunnel barriers into Co/h-BN/Fe magnetic tunnel junctions (MTJs). The h-BN monolayer is directly grown by chemical vapor deposition on Fe. The Conductive Tip Atomic Force Microscopy (CT-AFM) measurements reveal the homogeneity of the tunnel behavior of our h-BN layers. As expected for tunneling, the resistance depends exponentially on the number of h-BN layers. The h-BN monolayer properties are also characterized through integration into complete MTJ devices. A Tunnel Magnetoresistance of up to 6% is observed for a MTJ based on a single atomically thin h-BN layer.

  19. Spin tunnelling in mesoscopic systems

    Indian Academy of Sciences (India)

    We study spin tunnelling in molecular magnets as an instance of a mesoscopic phenomenon, with special emphasis on the molecule Fe8. We show that the tunnel splitting between various pairs of Zeeman levels in this molecule oscillates as a function of applied magnetic field, vanishing completely at special points in the ...

  20. Hawking temperature from tunnelling formalism

    OpenAIRE

    Mitra, P.

    2007-01-01

    It has recently been suggested that the attempt to understand Hawking radiation as tunnelling across black hole horizons produces a Hawking temperature double the standard value. It is explained here how one can obtain the standard value in the same tunnelling approach.

  1. Tunneling Ionization of Diatomic Molecules

    DEFF Research Database (Denmark)

    Svensmark, Jens Søren Sieg

    2016-01-01

    When a molecule is subject to a strong laser field, there is a probability that an electron can escape, even though the electrons are bound by a large potential barrier. This is possible because electrons are quantum mechanical in nature, and they are therefore able to tunnel through potential...... barriers, an ability classical particles do not possess. Tunnelling is a fundamental quantum mechanical process, a process that is distinctly non-classical, so solving this tunnelling problem is not only relevant for molecular physics, but also for quantum theory in general. In this dissertation the theory...... of tunneling ionizaion of molecules is presented and the results of numerical calculations are shown. One perhaps surprising result is, that the frequently used Born-Oppenheimer approximation breaks down for weak fields when describing tunneling ionization. An analytic theory applicable in the weak-field limit...

  2. Tunneling from the past horizon

    Science.gov (United States)

    Kang, Subeom; Yeom, Dong-han

    2018-04-01

    We investigate a tunneling and emission process of a thin-shell from a Schwarzschild black hole, where the shell was initially located beyond the Einstein-Rosen bridge and finally appears at the right side of the Penrose diagram. In order to obtain such a solution, we should assume that the areal radius of the black hole horizon increases after the tunneling. Hence, there is a parameter range such that the tunneling rate is exponentially enhanced, rather than suppressed. We may have two interpretations regarding this. First, such a tunneling process from the past horizon is improbable by physical reasons; second, such a tunneling is possible in principle, but in order to obtain a stable Einstein-Rosen bridge, one needs to restrict the parameter spaces. If such a process is allowed, this can be a nonperturbative contribution to Einstein-Rosen bridges as well as eternal black holes.

  3. Fluctuation Dominated Josephson Tunneling with a Scanning Tunneling Microscope

    International Nuclear Information System (INIS)

    Naaman, O.; Teizer, W.; Dynes, R. C.

    2001-01-01

    We demonstrate Josephson tunneling in vacuum tunnel junctions formed between a superconducting scanning tunneling microscope tip and a Pb film, for junction resistances in the range 50--300 k Omega. We show that the superconducting phase dynamics is dominated by thermal fluctuations, and that the Josephson current appears as a peak centered at small finite voltage. In the presence of microwave fields (f=15.0 GHz) the peak decreases in magnitude and shifts to higher voltages with increasing rf power, in agreement with theory

  4. Tunneling junction as an open system. Normal tunneling

    International Nuclear Information System (INIS)

    Ono, Y.

    1978-01-01

    The method of the tunneling Hamiltonian is reformulated in the case of normal tunneling by introducing two independent particle baths. Due to the baths, it becomes possible to realize a final stationary state where the electron numbers of the two electrodes in the tunneling system are maintained constant and where there exists a stationary current. The effect of the bath-system couplings on the current-voltage characteristics of the junction is discussed in relation to the usual expression of the current as a function of voltage. (Auth.)

  5. Frequency driven inversion of tunnel magnetoimpedance and observation of positive tunnel magnetocapacitance in magnetic tunnel junctions

    International Nuclear Information System (INIS)

    Parui, Subir; Ribeiro, Mário; Atxabal, Ainhoa; Llopis, Roger; Bedoya-Pinto, Amilcar; Sun, Xiangnan; Casanova, Fèlix; Hueso, Luis E.

    2016-01-01

    The relevance for modern computation of non-volatile high-frequency memories makes ac-transport measurements of magnetic tunnel junctions (MTJs) crucial for exploring this regime. Here, we demonstrate a frequency-mediated effect in which the tunnel magnetoimpedance reverses its sign in a classical Co/Al 2 O 3 /NiFe MTJ, whereas we only observe a gradual decrease in the tunnel magnetophase. Such effects are explained by the capacitive coupling of a parallel resistor and capacitor in the equivalent circuit model of the MTJ. Furthermore, we report a positive tunnel magnetocapacitance effect, suggesting the presence of a spin-capacitance at the two ferromagnet/tunnel-barrier interfaces. Our results are important for understanding spin transport phenomena at the high frequency regime in which the spin-polarized charge accumulation due to spin-dependent penetration depth at the two interfaces plays a crucial role.

  6. Frequency driven inversion of tunnel magnetoimpedance and observation of positive tunnel magnetocapacitance in magnetic tunnel junctions

    Energy Technology Data Exchange (ETDEWEB)

    Parui, Subir, E-mail: s.parui@nanogune.eu, E-mail: l.hueso@nanogune.eu; Ribeiro, Mário; Atxabal, Ainhoa; Llopis, Roger [CIC nanoGUNE, 20018 Donostia-San Sebastian (Spain); Bedoya-Pinto, Amilcar [CIC nanoGUNE, 20018 Donostia-San Sebastian (Spain); Max Planck Institute of Microstructure Physics, D-06120 Halle (Germany); Sun, Xiangnan [CIC nanoGUNE, 20018 Donostia-San Sebastian (Spain); National Center for Nanoscience and Technology, 100190 Beijing (China); Casanova, Fèlix; Hueso, Luis E., E-mail: s.parui@nanogune.eu, E-mail: l.hueso@nanogune.eu [CIC nanoGUNE, 20018 Donostia-San Sebastian (Spain); IKERBASQUE, Basque Foundation for Science, 48011 Bilbao (Spain)

    2016-08-01

    The relevance for modern computation of non-volatile high-frequency memories makes ac-transport measurements of magnetic tunnel junctions (MTJs) crucial for exploring this regime. Here, we demonstrate a frequency-mediated effect in which the tunnel magnetoimpedance reverses its sign in a classical Co/Al{sub 2}O{sub 3}/NiFe MTJ, whereas we only observe a gradual decrease in the tunnel magnetophase. Such effects are explained by the capacitive coupling of a parallel resistor and capacitor in the equivalent circuit model of the MTJ. Furthermore, we report a positive tunnel magnetocapacitance effect, suggesting the presence of a spin-capacitance at the two ferromagnet/tunnel-barrier interfaces. Our results are important for understanding spin transport phenomena at the high frequency regime in which the spin-polarized charge accumulation due to spin-dependent penetration depth at the two interfaces plays a crucial role.

  7. Carpal tunnel syndrome - Part II (treatment,

    Directory of Open Access Journals (Sweden)

    Michel Chammas

    2014-10-01

    Full Text Available The treatments for non-deficit forms of carpal tunnel syndrome (CTS are corticoid infiltration and/or a nighttime immobilization brace. Surgical treatment, which includes sectioning the retinaculum of the flexors (retinaculotomy, is indicated in cases of resistance to conservative treatment in deficit forms or, more frequently, in acute forms. In minimally invasive techniques (endoscopy and mini-open, and even though the learning curve is longer, it seems that functional recovery occurs earlier than in the classical surgery, but with identical long-term results. The choice depends on the surgeon, patient, severity, etiology and availability of material. The results are satisfactory in close to 90% of the cases. Recovery of strength requires four to six months after regression of the pain of pillar pain type. This surgery has the reputation of being benign and has a complication rate of 0.2–0.5%.

  8. Acupuncture for acute hordeolum

    Science.gov (United States)

    Cheng, Ke; Law, Andrew; Guo, Menghu; Wieland, L. Susan; Shen, Xueyong; Lao, Lixing

    2017-01-01

    Background Hordeolum is an acute, purulent inflammation of the eyelid margin usually caused by obstructed orifices of the sebaceous glands of the eyelid. The condition, which affects sebaceous glands internally or externally, is common. When the meibomian gland in the tarsal plate is affected, internal hordeolum occurs, while when the glands of Zeis or Moll associated with eyelash follicles are affected, external hordeolum, or stye occurs. The onset of hordeolum is usually self limited, and may resolve in about a week with spontaneous drainage of the abscess. When the condition is severe, it can spread to adjacent glands and tissues. Recurrences are very common. As long as an internal hordeolum remains unresolved, it can develop into a chalazion or generalized eyelid cellulitis. Acupuncture is a traditional Chinese medical therapy aimed to treat disease by using fine needles to stimulate specific points on the body. However, it is unclear if acupuncture is an effective and safe treatment for acute hordeolum. Objectives The objective of this review was to investigate the effectiveness and safety of acupuncture to treat acute hordeolum compared with no treatment, sham acupuncture, or other active treatment. We also compared the effectiveness and safety of acupuncture plus another treatment with that treatment alone. Search methods We searched CENTRAL, Ovid MEDLINE, Ovid MEDLINE In-Process and Other Non-Indexed Citations, Ovid MEDLINE Daily, Ovid OLDMEDLINE, Embase, PubMed, Latin American and Caribbean Health Sciences Literature Database (LILACS), three major Chinese databases, as well as clinical trial registers all through 7 June 2016. We reviewed the reference lists from potentially eligible studies to identify additional randomised clinical trials (RCTs). Selection criteria We included RCTs of people diagnosed with acute internal or external hordeola. We included RCTs comparing acupuncture with sham acupuncture or no treatment, other active treatments, or

  9. Tunneling of Atoms, Nuclei and Molecules

    International Nuclear Information System (INIS)

    Bertulani, C.A.

    2015-01-01

    This is a brief review of few relevant topics on tunneling of composite particles and how the coupling to intrinsic and external degrees of freedom affects tunneling probabilities. I discuss the phenomena of resonant tunneling, different barriers seen by subsystems, damping of resonant tunneling by level bunching and continuum effects due to particle dissociation. (author)

  10. Computational Multiqubit Tunnelling in Programmable Quantum Annealers

    Science.gov (United States)

    2016-08-25

    ARTICLE Received 3 Jun 2015 | Accepted 26 Nov 2015 | Published 7 Jan 2016 Computational multiqubit tunnelling in programmable quantum annealers...state itself. Quantum tunnelling has been hypothesized as an advantageous physical resource for optimization in quantum annealing. However, computational ...qubit tunnelling plays a computational role in a currently available programmable quantum annealer. We devise a probe for tunnelling, a computational

  11. 78 FR 46117 - National Tunnel Inspection Standards

    Science.gov (United States)

    2013-07-30

    ... busiest vehicular tunnel in the world. The Fort McHenry Tunnel handles a daily traffic volume of more than... vehicular, transit, and rail tunnels in the New York City metropolitan area. Although it is still too early... congestion along alternative routes, and save users both dollars and fuel. If these tunnels were closed due...

  12. Een systeem voor classificatie van korte tunnels.

    NARCIS (Netherlands)

    Schreuder, D.A.

    1985-01-01

    The most difficult problems in the lighting of tunnels occur in daylight and in particular in the entrance of the tunnel, while drivers approaching the tunnel must be able to look into the tunnel from the outside to detect the road course and eventual obstacles. A classification should The made on

  13. Tunnel fire testing and modeling the Morgex North tunnel experiment

    CERN Document Server

    Borghetti, Fabio; Gandini, Paolo; Frassoldati, Alessio; Tavelli, Silvia

    2017-01-01

    This book aims to cast light on all aspects of tunnel fires, based on experimental activities and theoretical and computational fluid dynamics (CFD) analyses. In particular, the authors describe a transient full-scale fire test (~15 MW), explaining how they designed and performed the experimental activity inside the Morgex North tunnel in Italy. The entire organization of the experiment is described, from preliminary evaluations to the solutions found for management of operational difficulties and safety issues. This fire test allowed the collection of different measurements (temperature, air velocity, smoke composition, pollutant species) useful for validating and improving CFD codes and for testing the real behavior of the tunnel and its safety systems during a diesel oil fire with a significant heat release rate. Finally, the fire dynamics are compared with empirical correlations, CFD simulations, and literature measurements obtained in other similar tunnel fire tests. This book will be of interest to all ...

  14. Apparent tunneling in chemical reactions

    DEFF Research Database (Denmark)

    Henriksen, Niels Engholm; Hansen, Flemming Yssing; Billing, G. D.

    2000-01-01

    A necessary condition for tunneling in a chemical reaction is that the probability of crossing a barrier is non-zero, when the energy of the reactants is below the potential energy of the barrier. Due to the non-classical nature (i.e, momentum uncertainty) of vibrational states this is, however......, not a sufficient condition in order to establish genuine tunneling as a result of quantum dynamics. This proposition is illustrated for a two-dimensional model potential describing dissociative sticking of N-2 on Ru(s). It is suggested that the remarkable heavy atom tunneling, found in this system, is related...

  15. Tunneling progress on the Yucca Mountain Project

    International Nuclear Information System (INIS)

    Hansmire, W.H.; Munzer, R.J.

    1996-01-01

    The current status of tunneling progress on the Yucca Mountain Project (YMP) is presented in this paper. The Exploratory Studies Facility (ESF), a key part of the YMP, has been long in development and construction is ongoing. This is a progress report on the tunneling aspects of the ESF as of January 1, 1996. For purposes of discussion in this summary, the tunneling has progressed in four general phases. The paper describes: tunneling in jointed rock under low stress; tunneling through the Bow Ridge Fault and soft rock; tunneling through the Imbricate Fault Zone; and Tunneling into the candidate repository formation

  16. Tunnel magnetoresistance in asymmetric double-barrier magnetic tunnel junctions

    International Nuclear Information System (INIS)

    Useinov, N.Kh.; Petukhov, D.A.; Tagirov, L.R.

    2015-01-01

    The spin-polarized tunnel conductance and tunnel magnetoresistance (TMR) through a planar asymmetric double-barrier magnetic tunnel junction (DBMTJ) have been calculated using quasi-classical model. In DBMTJ nanostructure the magnetization of middle ferromagnetic metal layer can be aligned parallel or antiparallel with respect to the fixed magnetizations of the top and bottom ferromagnetic electrodes. The transmission coefficients of an electron to pass through the barriers have been calculated in terms of quantum mechanics. The dependencies of tunnel conductance and TMR on the applied voltage have been calculated in case of non-resonant transmission. Estimated in the framework of our model, the difference between the spin-channels conductances at low voltages was found relatively large. This gives rise to very high magnitude of TMR. - Highlights: • The spin-polarized conductance through the junction is calculated. • Dependencies of the tunnel conductance vs applied bias are shown. • Bias voltage dependence of tunnel magnetoresistance for the structure is shown

  17. Tunneling through landsliding zone; Jisuberi chitainai no tunnel seko

    Energy Technology Data Exchange (ETDEWEB)

    Konbu, A; Hatabu, K; Kano, T [Tekken Corp., Tokyo (Japan)

    1994-08-01

    At the new tunnel construction site of the Shirakata tunnel on the Obama line in Yamaguchi Prefecture, a landsliding occurred at about 60 meters to the upper portion obliquely to the right hand side of the shaft when the excavation progressed to about 10 meters from the starting side. The landslide caused displacement at the shaft opening and change in the supports. As a result of the re-investigation, it was confirmed that the slide face went through the tunnel cross section. The measures taken were removal of the upper soil and an adoption of the all ground fastening (AGF) method (injection type long tip fastening method) as an auxiliary construction to stop loosening of the natural ground associated with the tunnel excavation. The result was a completion of tunneling the landsliding zone without a problem. This paper reports the AGF method adopted in the above construction, together with the construction works and natural ground conditions. The AGF method is about the same as the pipe roof method with regard to the natural ground accepting mechanism and the materials used. The difference is building an improved body in a limited area in the natural ground around the steel pipes by injecting the fixing material. The use of this method caused no problems in subsidence and displacement in the surrounding ground, and completed the tunneling construction without an unusual event. 1 ref., 7 figs., 2 tabs.

  18. FUNDAMENTAL TUNNELING PROCESSES IN MOSa SOLAR CELLS

    OpenAIRE

    Balberg , I.; Hanak , J.; Weakliem , H.; Gal , E.

    1981-01-01

    In previous studies of tunneling through a MOSa tunnel junction, where Sa was a-Si : H, it was shown that their characteristics resemble those of MOSc devices where Sc was crystalline silicon. In the present work we would like to report a demonstration of fundamental tunneling processes in such tunnel junctions. In particular, the transition from semiconductor controlled regime to tunneling controlled regime can be clearly distinguished. The present results represent one of the rare cases whe...

  19. Destructive quantum interference in spin tunneling problems

    OpenAIRE

    von Delft, Jan; Henley, Christopher L.

    1992-01-01

    In some spin tunneling problems, there are several different but symmetry-related tunneling paths that connect the same initial and final configurations. The topological phase factors of the corresponding tunneling amplitudes can lead to destructive interference between the different paths, so that the total tunneling amplitude is zero. In the study of tunneling between different ground state configurations of the Kagom\\'{e}-lattice quantum Heisenberg antiferromagnet, this occurs when the spi...

  20. 13th Australian tunnelling conference. Proceedings

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2008-07-01

    The theme of the conference was 'Engineering in a changing environment'. Topics covered include Australian tunnelling projects, design and development of ground support, tunnelling, international projects, fire and life safety, mining projects, risk management in tunnelling, and tunnel boring machine tunnelling. Papers of particular interest to the coal industry are: improving roadway development in underground coal mine (G. Lewis and G. Gibson), and polymer-based alternative to steel mesh for coal mine strata reinforcement (C. Lukey and others).

  1. Tunnelling instability via perturbation theory

    Energy Technology Data Exchange (ETDEWEB)

    Graffi, S. (Bologna Univ. (Italy). Dip. di Matematica); Grecchi, V. (Moderna Univ. (Italy). Dip. di Matematica); Jona-Lasinio, G. (Paris-11 Univ., 91 - Orsay (France). Lab. de Physique Theorique et Hautes Energies)

    1984-10-21

    The semiclassical limit of low lying states in a multiwell potential is studied by rigorous perturbative techniques. In particular tunnelling instability and localisation of wave functions is obtained in a simple way under small deformations of symmetric potentials.

  2. Scanning Tunneling Microscopy - image interpretation

    International Nuclear Information System (INIS)

    Maca, F.

    1998-01-01

    The basic ideas of image interpretation in Scanning Tunneling Microscopy are presented using simple quantum-mechanical models and supplied with examples of successful application. The importance is stressed of a correct interpretation of this brilliant experimental surface technique

  3. Electron tunneling in proteins program.

    Science.gov (United States)

    Hagras, Muhammad A; Stuchebrukhov, Alexei A

    2016-06-05

    We developed a unique integrated software package (called Electron Tunneling in Proteins Program or ETP) which provides an environment with different capabilities such as tunneling current calculation, semi-empirical quantum mechanical calculation, and molecular modeling simulation for calculation and analysis of electron transfer reactions in proteins. ETP program is developed as a cross-platform client-server program in which all the different calculations are conducted at the server side while only the client terminal displays the resulting calculation outputs in the different supported representations. ETP program is integrated with a set of well-known computational software packages including Gaussian, BALLVIEW, Dowser, pKip, and APBS. In addition, ETP program supports various visualization methods for the tunneling calculation results that assist in a more comprehensive understanding of the tunneling process. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  4. Tunneling Plasmonics in Bilayer Graphene.

    Science.gov (United States)

    Fei, Z; Iwinski, E G; Ni, G X; Zhang, L M; Bao, W; Rodin, A S; Lee, Y; Wagner, M; Liu, M K; Dai, S; Goldflam, M D; Thiemens, M; Keilmann, F; Lau, C N; Castro-Neto, A H; Fogler, M M; Basov, D N

    2015-08-12

    We report experimental signatures of plasmonic effects due to electron tunneling between adjacent graphene layers. At subnanometer separation, such layers can form either a strongly coupled bilayer graphene with a Bernal stacking or a weakly coupled double-layer graphene with a random stacking order. Effects due to interlayer tunneling dominate in the former case but are negligible in the latter. We found through infrared nanoimaging that bilayer graphene supports plasmons with a higher degree of confinement compared to single- and double-layer graphene, a direct consequence of interlayer tunneling. Moreover, we were able to shut off plasmons in bilayer graphene through gating within a wide voltage range. Theoretical modeling indicates that such a plasmon-off region is directly linked to a gapped insulating state of bilayer graphene, yet another implication of interlayer tunneling. Our work uncovers essential plasmonic properties in bilayer graphene and suggests a possibility to achieve novel plasmonic functionalities in graphene few-layers.

  5. Shaft and tunnel sealing considerations

    International Nuclear Information System (INIS)

    Kelsall, P.C.; Shukla, D.K.

    1980-01-01

    Much of the emphasis of previous repository sealing research has been placed on plugging small diameter boreholes. It is increasingly evident that equal emphasis should now be given to shafts and tunnels which constitute more significant pathways between a repository and the biosphere. The paper discusses differences in requirements for sealing shafts and tunnels as compared with boreholes and the implications for seal design. Consideration is given to a design approach for shaft and tunnel seals based on a multiple component design concept, taking into account the requirements for retrievability of the waste. A work plan is developed for the future studies required to advance shaft and tunnel sealing technology to a level comparable with the existing technology for borehole sealing

  6. Organic tunnel field effect transistors

    KAUST Repository

    Tietze, Max Lutz; Lussem, Bjorn; Liu, Shiyi

    2017-01-01

    Various examples are provided for organic tunnel field effect transistors (OTFET), and methods thereof. In one example, an OTFET includes a first intrinsic layer (i-layer) of organic semiconductor material disposed over a gate insulating layer

  7. Bijzondere belastingen in tunnels : Eindrapport

    NARCIS (Netherlands)

    Molenaar, D.J.; Weerheijm, J.; Vervuurt, A.; Burggraaf, H.; Roekaerts, D.; Meijers, P.

    2009-01-01

    Verkeerstunnels en overkapte wegen (landtunnels) komen de milieukundige en stedenbouwkundige inpassing ten goede en maken meervoudig ruimtegebruik in de stad mogelijk. Het aantal tunnels en overkappingen groeit dan ook. Dit maakt het vervoer van explosiegevaarlijke stoffen en onder hoge druk

  8. Free Surface Water Tunnel (FSWT)

    Data.gov (United States)

    Federal Laboratory Consortium — Description: The Free Surface Water Tunnel consists of the intake plenum, the test section and the exit plenum. The intake plenum starts with a perforated pipe that...

  9. Direct, coherent and incoherent intermediate state tunneling and scanning tunnel microscopy (STM)

    International Nuclear Information System (INIS)

    Halbritter, J.

    1997-01-01

    Theory and experiment in tunneling are still qualitative in nature, which hold true also for the latest developments in direct-, resonant-, coherent- and incoherent-tunneling. Those tunnel processes have recently branched out of the field of ''solid state tunnel junctions'' into the fields of scanning tunnel microscopy (STM), single electron tunneling (SET) and semiconducting resonant tunnel structures (RTS). All these fields have promoted the understanding of tunneling in different ways reaching from the effect of coherence, of incoherence and of charging in tunneling, to spin flip or inelastic effects. STM allows not only the accurate measurements of the tunnel current and its voltage dependence but, more importantly, the easy quantification via the (quantum) tunnel channel conductance and the distance dependence. This new degree of freedom entering exponentially the tunnel current allows an unique identification of individual tunnel channels and their quantification. In STM measurements large tunnel currents are observed for large distances d > 1 nm explainable by intermediate state tunneling. Direct tunneling with its reduced tunnel time and reduced off-site Coulomb charging bridges distances below 1 nm, only. The effective charge transfer process with its larger off-site and on-site charging at intermediate states dominates tunnel transfer in STM, biology and chemistry over distances in the nm-range. Intermediates state tunneling becomes variable range hopping conduction for distances larger than d > 2 nm, for larger densities of intermediate states n 1 (ε) and for larger temperatures T or voltages U, still allowing high resolution imaging

  10. Quantum resonances in physical tunneling

    International Nuclear Information System (INIS)

    Nieto, M.M.; Truax, D.R.

    1985-01-01

    It has recently been emphasized that the probability of quantum tunneling is a critical function of the shape of the potential. Applying this observation to physical systems, we point out that in principal information on potential surfaces can be obtained by studying tunneling rates. This is especially true in cases where only spectral data is known, since many potentials yield the same spectrum. 13 refs., 10 figs., 1 tab

  11. Human eyelid meibomian glands and tarsal muscle are recognized by autoantibodies from patients affected by a new variant of endemic pemphigus foliaceus in El-Bagre, Colombia, South America.

    Science.gov (United States)

    Abreu-Velez, Ana Maria; Howard, Michael S; Hashimoto, Takashi; Grossniklaus, Hans E

    2010-03-01

    Previously, we described a new variant of endemic pemphigus foliaceus (EPF) in Colombia, South America (El Bagre-EPF). Continuing our characterization of this variant of EPF, we now focus on one of our previously reported clinical findings: the presence of ocular lesions. These ocular lesions are seen in patients having extensive skin involvement, as measured by the Lund and Browder scale, which is generally used for patients with skin burns. We specifically searched for evidence of autoreactivity to various eyelid structures in these patients and correlated our immunologic data with the clinical findings. We performed indirect immunofluorescence studies using normal-appearing human eyelid skin from routine blepharoplasties as substrate tissue. We tested sera from 12 patients with El Bagre-EPF and ocular lesions, 5 patients with sporadic (nonendemic) pemphigus foliaceus, and 20 healthy control subjects (10 from the El Bagre-EPF endemic area and 10 from nonendemic areas). We used fluorescein isothiocyanate conjugated goat antiserum to human total IgG/IgA/IgM as a secondary antibody. In addition, we used fluorescein isothiocyanate conjugated antibodies to human fibrinogen, albumin, IgG, IgE, C1q, and C3, Texas Red (Rockland Immunochemicals, Inc, Gilbertsville, PA), Alexa Fluor 555, or Alexa Fluor 594 (Invitrogen, Carlsbad, CA). Ki-67 (a cell proliferation marker) was used to determine the cell proliferation rate, and nuclear counterstaining was performed with either 4', 6-diamidino-2-phenylindole or Topro III (Invitrogen, Carlsbad, CA). We observed autoreactivity to multiple eyelid structures, including meibomian glands and tarsal muscle bundles at different levels, and some areas of the epidermis and the dermis close to the isthmus of the eyelids. Tarsal plate autoreactivity was seen in 10 of 12 of the El Bagre-EPF sera and in one control with pemphigus erythematosus. Furthermore, immunoprecipitation using an eyelid sample as a substrate with 1 mmol/L of sodium

  12. Tunnelling without barriers

    International Nuclear Information System (INIS)

    Lee, K.

    1987-01-01

    The evolution in flat and curved space-time of quantum fields in theories with relative flat potential and its consequences are considered. It is shown that bubble nucleation, a quantum mechanical tunnelling process, may occur in flat space-time, having a bounce solution, even if V(phi) has no barrier. It is shown that bubble nucleation can also occur in curved space-time even though there is no bounce solution in the standard formalism for the bubble nucleation rate in curved space-time. Additionally, bubbles can nucleate during the slow rolling period on the potential in flat and curved space-time, in this case also there is no bounce solution. It is known in the new inflationary scenario that energy density perturbations caused by quantum fluctuations of the scalar field can satisfy the presently observed bounds on density perturbations. Bubble nucleation during the slow rolling period also gives rise to density perturbations. For a model potential density perturbations by bubbles are calculated at the horizon reentering. By applying the bound from the almost isotropic microwave black body radiation on these density perturbations, a constraint on the model potential is obtained. Finally, some further implications on the galaxy formation and applications in more realistic potential are discussed

  13. Scanning Tunneling Optical Resonance Microscopy

    Science.gov (United States)

    Bailey, Sheila; Wilt, Dave; Raffaelle, Ryne; Gennett, Tom; Tin, Padetha; Lau, Janice; Castro, Stephanie; Jenkins, Philip; Scheiman, Dave

    2003-01-01

    Scanning tunneling optical resonance microscopy (STORM) is a method, now undergoing development, for measuring optoelectronic properties of materials and devices on the nanoscale by means of a combination of (1) traditional scanning tunneling microscopy (STM) with (2) tunable laser spectroscopy. In STORM, an STM tip probing a semiconductor is illuminated with modulated light at a wavelength in the visible-to-near-infrared range and the resulting photoenhancement of the tunneling current is measured as a function of the illuminating wavelength. The photoenhancement of tunneling current occurs when the laser photon energy is sufficient to excite charge carriers into the conduction band of the semiconductor. Figure 1 schematically depicts a proposed STORM apparatus. The light for illuminating the semiconductor specimen at the STM would be generated by a ring laser that would be tunable across the wavelength range of interest. The laser beam would be chopped by an achromatic liquid-crystal modulator. A polarization-maintaining optical fiber would couple the light to the tip/sample junction of a commercial STM. An STM can be operated in one of two modes: constant height or constant current. A STORM apparatus would be operated in the constant-current mode, in which the height of the tip relative to the specimen would be varied in order to keep the tunneling current constant. In this mode, a feedback control circuit adjusts the voltage applied to a piezoelectric actuator in the STM that adjusts the height of the STM tip to keep the tunneling current constant. The exponential relationship between the tunneling current and tip-to-sample distance makes it relatively easy to implement this mode of operation. The choice of method by which the photoenhanced portion of the tunneling current would be measured depends on choice of the frequency at which the input illumination would be modulated (chopped). If the frequency of modulation were low enough (typically tunneling current

  14. Electronic noise of superconducting tunnel junction detectors

    International Nuclear Information System (INIS)

    Jochum, J.; Kraus, H.; Gutsche, M.; Kemmather, B.; Feilitzsch, F. v.; Moessbauer, R.L.

    1994-01-01

    The optimal signal to noise ratio for detectors based on superconducting tunnel junctions is calculated and compared for the cases of a detector consisting of one single tunnel junction, as well as of series and of parallel connections of such tunnel junctions. The influence of 1 / f noise and its dependence on the dynamical resistance of tunnel junctions is discussed quantitatively. A single tunnel junction yields the minimum equivalent noise charge. Such a tunnel junction exhibits the best signal to noise ratio if the signal charge is independent of detector size. In case, signal charge increases with detector size, a parallel or a series connection of tunnel junctions would provide the optimum signal to noise ratio. The equivalent noise charge and the respective signal to noise ratio are deduced as functions of tunnel junction parameters such as tunneling time, quasiparticle lifetime, etc. (orig.)

  15. Theory of superconducting tunneling without the tunneling Hamiltonian

    International Nuclear Information System (INIS)

    Arnold, G.B.

    1987-01-01

    When a tunneling barrier is nearly transparent, the standard tunneling (or transfer) Hamiltonian approximation fails. The author describes the theory which is necessary for calculating the tunneling current in these cases, and illustrate it by comparing theory and experiment on superconductor/insulator/superconductor (SIS) junctions have ultra-thin tunnel barriers. This theory accurately explains the subgap structure which appears in the dynamical resistance of such SIS junctions, including many observed details which no previous theory has reproduced. The expression for the current through an SIS junction with an ultrathin barrier is given by I(t) = Re{Sigma/sub n/ J/sub n/ (omega/sub o/)e/sup in omega/o/sup t/} where omega/sub o/ = 2eV/h is the Josephson frequency, V is the bias voltage, and the J/sub n/ are voltage dependent coefficients, one for each positive or negative integer, n, and n=0. The relative sign of the terms involving cos(n omega/sub o/t) and sin(n omega/sub o/t) agrees with experiment, in contrast to previous theories of Josephson tunneling

  16. Improved multidimensional semiclassical tunneling theory.

    Science.gov (United States)

    Wagner, Albert F

    2013-12-12

    We show that the analytic multidimensional semiclassical tunneling formula of Miller et al. [Miller, W. H.; Hernandez, R.; Handy, N. C.; Jayatilaka, D.; Willets, A. Chem. Phys. Lett. 1990, 172, 62] is qualitatively incorrect for deep tunneling at energies well below the top of the barrier. The origin of this deficiency is that the formula uses an effective barrier weakly related to the true energetics but correctly adjusted to reproduce the harmonic description and anharmonic corrections of the reaction path at the saddle point as determined by second order vibrational perturbation theory. We present an analytic improved semiclassical formula that correctly includes energetic information and allows a qualitatively correct representation of deep tunneling. This is done by constructing a three segment composite Eckart potential that is continuous everywhere in both value and derivative. This composite potential has an analytic barrier penetration integral from which the semiclassical action can be derived and then used to define the semiclassical tunneling probability. The middle segment of the composite potential by itself is superior to the original formula of Miller et al. because it incorporates the asymmetry of the reaction barrier produced by the known reaction exoergicity. Comparison of the semiclassical and exact quantum tunneling probability for the pure Eckart potential suggests a simple threshold multiplicative factor to the improved formula to account for quantum effects very near threshold not represented by semiclassical theory. The deep tunneling limitations of the original formula are echoed in semiclassical high-energy descriptions of bound vibrational states perpendicular to the reaction path at the saddle point. However, typically ab initio energetic information is not available to correct it. The Supporting Information contains a Fortran code, test input, and test output that implements the improved semiclassical tunneling formula.

  17. Superconducting tunneling with the tunneling Hamiltonian. II. Subgap harmonic structure

    International Nuclear Information System (INIS)

    Arnold, G.B.

    1987-01-01

    The theory of superconducting tunneling without the tunneling Hamiltonian is extended to treat superconductor/insulator/superconductor junctions in which the transmission coefficient of the insulating barrier approaches unity. The solution for the current in such junctions is obtained by solving the problem of a particle hopping in a one-dimensional lattice of sites, with forward and reverse transfer integrals that depend on the site. The results are applied to the problem of subgap harmonic structure in superconducting tunneling. The time-dependent current at finite voltage through a junction exhibiting subgap structure is found to have terms that oscillate at all integer multiples of the Josephson frequency, n(2eV/h). The amplitudes of these new, and as yet unmeasured, ac current contributions as a function of voltage are predicted

  18. Typical Underwater Tunnels in the Mainland of China and Related Tunneling Technologies

    Directory of Open Access Journals (Sweden)

    Kairong Hong

    2017-12-01

    Full Text Available In the past decades, many underwater tunnels have been constructed in the mainland of China, and great progress has been made in related tunneling technologies. This paper presents the history and state of the art of underwater tunnels in the mainland of China in terms of shield-bored tunnels, drill-and-blast tunnels, and immersed tunnels. Typical underwater tunnels of these types in the mainland of China are described, along with innovative technologies regarding comprehensive geological prediction, grouting-based consolidation, the design and construction of large cross-sectional tunnels with shallow cover in weak strata, cutting tool replacement under limited drainage and reduced pressure conditions, the detection and treatment of boulders, the construction of underwater tunnels in areas with high seismic intensity, and the treatment of serious sedimentation in a foundation channel of immersed tunnels. Some suggestions are made regarding the three potential great strait-crossing tunnels—the Qiongzhou Strait-Crossing Tunnel, Bohai Strait-Crossing Tunnel, and Taiwan Strait-Crossing Tunnel—and issues related to these great strait-crossing tunnels that need further study are proposed. Keywords: Underwater tunnel, Strait-crossing tunnel, Shield-bored tunnel, Immersed tunnel, Drill and blast

  19. Current noise in tunnel junctions

    Energy Technology Data Exchange (ETDEWEB)

    Frey, Moritz; Grabert, Hermann [Physikalisches Institut, Universitaet Freiburg, Hermann-Herder-Strasse 3, 79104, Freiburg (Germany)

    2017-06-15

    We study current fluctuations in tunnel junctions driven by a voltage source. The voltage is applied to the tunneling element via an impedance providing an electromagnetic environment of the junction. We use circuit theory to relate the fluctuations of the current flowing in the leads of the junction with the voltage fluctuations generated by the environmental impedance and the fluctuations of the tunneling current. The spectrum of current fluctuations is found to consist of three parts: a term arising from the environmental Johnson-Nyquist noise, a term due to the shot noise of the tunneling current and a third term describing the cross-correlation between these two noise sources. Our phenomenological theory reproduces previous results based on the Hamiltonian model for the dynamical Coulomb blockade and provides a simple understanding of the current fluctuation spectrum in terms of circuit theory and properties of the average current. Specific results are given for a tunnel junction driven through a resonator. (copyright 2016 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  20. Superconducting tunnel-junction refrigerator

    International Nuclear Information System (INIS)

    Melton, R.G.; Paterson, J.L.; Kaplan, S.B.

    1980-01-01

    The dc current through an S 1 -S 2 tunnel junction, with Δ 2 greater than Δ 1 , when biased with eV 1 +Δ 2 , will lower the energy in S 1 . This energy reduction will be shared by the phonons and electrons. This device is shown to be analogous to a thermoelectric refrigerator with an effective Peltier coefficient π* approx. Δ 1 /e. Tunneling calculations yield the cooling power P/sub c/, the electrical power P/sub e/ supplied by the bias supply, and the cooling efficiency eta=P/sub c//P/sub e/. The maximum cooling power is obtained for eV= +- (Δ 2 -Δ 1 ) and t 1 =T 1 /T/sub c/1 approx. 0.9. Estimates are made of the temperature difference T 2 -T 1 achievable in Al-Pb and Sn-Pb junctions with an Al 2 O 3 tunneling barrier. The performance of this device is shown to yield a maximum cooling efficiency eta approx. = Δ 1 /(Δ 2 -Δ 1 ) which can be compared with that available in an ideal Carnot refrigerator of eta=T 1 /(T 2 -T 1 ). The development of a useful tunnel-junction refrigerator requires a tunneling barrier with an effective thermal conductance per unit area several orders of magnitude less than that provided by the A1 2 O 3 barrier in the Al-Pb and Sn-Pb systems

  1. TunnelVision: LHC Tunnel Photogrammetry System for Structural Monitoring

    CERN Document Server

    Fallas, William

    2014-01-01

    In this document an algorithm to detect deformations in the LHC Tunnel of CERN is presented. It is based on two images, one represents the ideal state of the tunnel and the other one the actual state. To find the differences between both, the algorithm is divided in three steps. First, an image enhancement is applied to make easier the detection. Second, two different approaches to reduce noise are applied to one or both images. And third, it is defined a group of characteristics about the type of deformation desired to detect. Finally, the conclusions show the effectiveness of the algorithm in the experimental results.

  2. Hybrid inflation exit through tunneling

    International Nuclear Information System (INIS)

    Garbrecht, Bjoern; Konstandin, Thomas

    2007-01-01

    For hybrid inflationary potentials, we derive the tunneling rate from field configurations along the flat direction towards the waterfall regime. This process competes with the classically rolling evolution of the scalar fields and needs to be strongly subdominant for phenomenologically viable models. Tunneling may exclude models with a mass scale below 10 12 GeV, but can be suppressed by small values of the coupling constants. We find that tunneling is negligible for those models, which do not require fine tuning in order to cancel radiative corrections, in particular for GUT-scale SUSY inflation. In contrast, electroweak scale hybrid inflation is not viable, unless the inflaton-waterfall field coupling is smaller than approximately 10 -11

  3. Effect of acute irradiation on the development of limbs in sheep

    Energy Technology Data Exchange (ETDEWEB)

    Rajtova, V [Institut fuer Normale Anatomie der Hochschule fuer Veterinaermedizin, Kosice, Czechoslovakia; Horak, J

    1976-01-01

    The effect of acute irradiation on the limb development in sheep was studied. The pelvic area of a pregnant sheep was irradiated locally on the 28th, 29th and 30th days after fertilization. The fetus was removed on the 15th day after irradiation and treated histologically. A single exposure with 250 R (higher exposures killed the fetus) was found to cease the limb development on the 28th day after irradiation (the critical period of the sheep limb development), to induce persistence of the intermedial ray on the 29th and 30th days, an early disappearance of the side finger rays, an early disappearance, fusion or deformation of some carpal and tarsal elements on the 29th and the 30th days after irradiation.

  4. The effect of acute irradiation on the development of limbs in sheep

    International Nuclear Information System (INIS)

    Rajtova, V.; Horak, J.

    1976-01-01

    The effect of acute irradiation on the limb development in sheep was studied. The pelvic area of a pregnant sheep was irradiated locally on the 28th, 29th and 30th days after fertilization. The fetus was removed on the 15th day after irradiation and treated histologically. A single exposure with 250 R (higher exposures killed the fetus) was found to cease the limb development on the 28th day after irradiation (the critical period of the sheep limb development), to induce persistence of the intermedial ray on the 29th and 30th days, an early disappearance of the side finger rays, an early disappearance, fusion or deformation of some carpal and tarsal elements on the 29th and the 30th days after irradiation. (author)

  5. Quantum mechanical tunneling in chemical physics

    CERN Document Server

    Nakamura, Hiroki

    2016-01-01

    Quantum mechanical tunneling plays important roles in a wide range of natural sciences, from nuclear and solid-state physics to proton transfer and chemical reactions in chemistry and biology. Responding to the need for further understanding of multidimensional tunneling, the authors have recently developed practical methods that can be applied to multidimensional systems. Quantum Mechanical Tunneling in Chemical Physics presents basic theories, as well as original ones developed by the authors. It also provides methodologies and numerical applications to real molecular systems. The book offers information so readers can understand the basic concepts and dynamics of multidimensional tunneling phenomena and use the described methods for various molecular spectroscopy and chemical dynamics problems. The text focuses on three tunneling phenomena: (1) energy splitting, or tunneling splitting, in symmetric double well potential, (2) decay of metastable state through tunneling, and (3) tunneling effects in chemical...

  6. Tunnel Boring Machine Performance Study. Final Report

    Science.gov (United States)

    1984-06-01

    Full face tunnel boring machine "TBM" performance during the excavation of 6 tunnels in sedimentary rock is considered in terms of utilization, penetration rates and cutter wear. The construction records are analyzed and the results are used to inves...

  7. Transit time for resonant tunneling

    International Nuclear Information System (INIS)

    Garcia Calderon, G.; Rubio, A.

    1990-09-01

    This work considers properties of the partial widths in one dimensional elastic resonant tunneling in order to propose a transit-time τ tr = (h/2π)/Γ n T res ) where Γ n is the elastic width and T res the transmission coefficient at resonance energy. This time is interpreted as an average over the resonance energy width. It is shown that the tunneling current density integrated across a sharp resonance is inversely proportional to τ tr . This transit time may be much larger than the values predicted by other definitions. (author). 20 refs

  8. Spin tunnelling in mesoscopic systems

    Science.gov (United States)

    Garg, Anupam

    2001-02-01

    We study spin tunnelling in molecular magnets as an instance of a mesoscopic phenomenon, with special emphasis on the molecule Fe8. We show that the tunnel splitting between various pairs of Zeeman levels in this molecule oscillates as a function of applied magnetic field, vanishing completely at special points in the space of magnetic fields, known as diabolical points. This phenomena is explained in terms of two approaches, one based on spin-coherent-state path integrals, and the other on a generalization of the phase integral (or WKB) method to difference equations. Explicit formulas for the diabolical points are obtained for a model Hamiltonian.

  9. Tunneling field effect transistor technology

    CERN Document Server

    Chan, Mansun

    2016-01-01

    This book provides a single-source reference to the state-of-the art in tunneling field effect transistors (TFETs). Readers will learn the TFETs physics from advanced atomistic simulations, the TFETs fabrication process and the important roles that TFETs will play in enabling integrated circuit designs for power efficiency. · Provides comprehensive reference to tunneling field effect transistors (TFETs); · Covers all aspects of TFETs, from device process to modeling and applications; · Enables design of power-efficient integrated circuits, with low power consumption TFETs.

  10. Inelastic scattering in resonant tunneling

    DEFF Research Database (Denmark)

    Wingreen, Ned S.; Jacobsen, Karsten Wedel; Wilkins, John W.

    1989-01-01

    The exact resonant-tunneling transmission probability for an electron interacting with phonons is presented in the limit that the elastic coupling to the leads is independent of energy. The phonons produce transmission sidebands but do not affect the integrated transmission probability or the esc......The exact resonant-tunneling transmission probability for an electron interacting with phonons is presented in the limit that the elastic coupling to the leads is independent of energy. The phonons produce transmission sidebands but do not affect the integrated transmission probability...

  11. Molecular series-tunneling junctions.

    Science.gov (United States)

    Liao, Kung-Ching; Hsu, Liang-Yan; Bowers, Carleen M; Rabitz, Herschel; Whitesides, George M

    2015-05-13

    Charge transport through junctions consisting of insulating molecular units is a quantum phenomenon that cannot be described adequately by classical circuit laws. This paper explores tunneling current densities in self-assembled monolayer (SAM)-based junctions with the structure Ag(TS)/O2C-R1-R2-H//Ga2O3/EGaIn, where Ag(TS) is template-stripped silver and EGaIn is the eutectic alloy of gallium and indium; R1 and R2 refer to two classes of insulating molecular units-(CH2)n and (C6H4)m-that are connected in series and have different tunneling decay constants in the Simmons equation. These junctions can be analyzed as a form of series-tunneling junctions based on the observation that permuting the order of R1 and R2 in the junction does not alter the overall rate of charge transport. By using the Ag/O2C interface, this system decouples the highest occupied molecular orbital (HOMO, which is localized on the carboxylate group) from strong interactions with the R1 and R2 units. The differences in rates of tunneling are thus determined by the electronic structure of the groups R1 and R2; these differences are not influenced by the order of R1 and R2 in the SAM. In an electrical potential model that rationalizes this observation, R1 and R2 contribute independently to the height of the barrier. This model explicitly assumes that contributions to rates of tunneling from the Ag(TS)/O2C and H//Ga2O3 interfaces are constant across the series examined. The current density of these series-tunneling junctions can be described by J(V) = J0(V) exp(-β1d1 - β2d2), where J(V) is the current density (A/cm(2)) at applied voltage V and βi and di are the parameters describing the attenuation of the tunneling current through a rectangular tunneling barrier, with width d and a height related to the attenuation factor β.

  12. Watertightness of concrete tunnel structures

    OpenAIRE

    Glerum, A.

    1982-01-01

    The Netherlands are situated in the delta. of the rivers Rhine, Meuse and Scheldt. Therefore the ground mainly consists.of sediments, such as sand, clay and silt. In certain regions peat layers of varying thickness are found. The high permeability of some of these materials and the fact that the groundwater table is generally only 1 m below ground level, make an adequate watertightness one of the main features of tunnel engineering in the Netherlands. Tunnels in Holland are both of the immers...

  13. Enhanced tunneling through nonstationary barriers

    International Nuclear Information System (INIS)

    Palomares-Baez, J. P.; Rodriguez-Lopez, J. L.; Ivlev, B.

    2007-01-01

    Quantum tunneling through a nonstationary barrier is studied analytically and by a direct numerical solution of Schroedinger equation. Both methods are in agreement and say that the main features of the phenomenon can be described in terms of classical trajectories which are solutions of Newton's equation in complex time. The probability of tunneling is governed by analytical properties of a time-dependent perturbation and the classical trajectory in the plane of complex time. Some preliminary numerical calculations of Euclidean resonance (an easy penetration through a classical nonstationary barrier due to an underbarrier interference) are presented

  14. Drill and blast tunnelling; Konvensjonell drift av tunneler

    Energy Technology Data Exchange (ETDEWEB)

    Roenn, Paal-Egil

    1997-12-31

    This thesis treats drill and blast tunnelling. The rapid technological advance necessitates revised and updated design criteria, quality requirements and quality control. In situ blast experiments were carried out in order to test new methods and improve the basis for calculation and design. The main topics of the experiments were (1) longer rounds and increased drillhole diameter, (2) emulsion slurry as explosives in tunnelling, and (3) electronic detonators in contour blasting. The experiments show that it is technically feasible to blast rounds of up to 8.6 m length. Using current technology, the economical optimum round length is substantially shorter. Dust, low visibility, noise and toxic fumes are occupational environmental strains for the tunnel workers. Several of the environmental factors are strongly influenced by the type of explosives used. For example, emulsion slurry resulted in 4 to 5 times better visibility than Anolit and the concentration of respirable dust and total dust was reduced by 30-50 %. Electronic detonators were tested and found to give a higher percentage of remaining drillholes in the contour than Nonel detonators. The thesis includes a chapter on economic design of hydropower tunnels. 42 refs., 83 figs., 45 tabs.

  15. Spin-dependent tunnelling in magnetic tunnel junctions

    International Nuclear Information System (INIS)

    Tsymbal, Evgeny Y; Mryasov, Oleg N; LeClair, Patrick R

    2003-01-01

    The phenomenon of electron tunnelling has been known since the advent of quantum mechanics, but continues to enrich our understanding of many fields of physics, as well as creating sub-fields on its own. Spin-dependent tunnelling (SDT) in magnetic tunnel junctions (MTJs) has recently aroused enormous interest and has developed in a vigorous field of research. The large tunnelling magnetoresistance (TMR) observed in MTJs garnered much attention due to possible applications in non-volatile random-access memories and next-generation magnetic field sensors. This led to a number of fundamental questions regarding the phenomenon of SDT. In this review article we present an overview of this field of research. We discuss various factors that control the spin polarization and magnetoresistance in MTJs. Starting from early experiments on SDT and their interpretation, we consider thereafter recent experiments and models which highlight the role of the electronic structure of the ferromagnets, the insulating layer, and the ferromagnet/insulator interfaces. We also discuss the role of disorder in the barrier and in the ferromagnetic electrodes and their influence on TMR. (topical review)

  16. Characterization of magnetic tunnel junction test pads

    DEFF Research Database (Denmark)

    Østerberg, Frederik Westergaard; Kjær, Daniel; Nielsen, Peter Folmer

    2015-01-01

    We show experimentally as well as theoretically that patterned magnetic tunnel junctions can be characterized using the current-in-plane tunneling (CIPT) method, and the key parameters, the resistance-area product (RA) and the tunnel magnetoresistance (TMR), can be determined. The CIPT method...

  17. Tunnel Face Stability & New CPT Applications

    NARCIS (Netherlands)

    Broere, W.

    2001-01-01

    Nearly all tunnels bored in soft soils have encountered problems with the stability of the tunnel face. In several cases these problems led to an extended stand-still of the boring process. A better understanding of the face stability, and of the soil conditions around the tunnel boring machine, can

  18. Tunneling into quantum wires: regularization of the tunneling Hamiltonian and consistency between free and bosonized fermions

    OpenAIRE

    Filippone, Michele; Brouwer, Piet

    2016-01-01

    Tunneling between a point contact and a one-dimensional wire is usually described with the help of a tunneling Hamiltonian that contains a delta function in position space. Whereas the leading order contribution to the tunneling current is independent of the way this delta function is regularized, higher-order corrections with respect to the tunneling amplitude are known to depend on the regularization. Instead of regularizing the delta function in the tunneling Hamiltonian, one may also obta...

  19. Macroscopic quantum tunneling in Josephson tunnel junctions and Coulomb blockade in single small tunnel junctions

    International Nuclear Information System (INIS)

    Cleland, A.N.

    1991-04-01

    Experiments investigating the process of macroscopic quantum tunneling in a moderately-damped, resistively shunted, Josephson junction are described, followed by a discussion of experiments performed on very small capacitance normal-metal tunnel junctions. The experiments on the resistively-shunted Josephson junction were designed to investigate a quantum process, that of the tunneling of the Josephson phase variable under a potential barrier, in a system in which dissipation plays a major role in the dynamics of motion. All the parameters of the junction were measured using the classical phenomena of thermal activation and resonant activation. Theoretical predictions are compared with the experimental results, showing good agreement with no adjustable parameters; the tunneling rate in the moderately damped (Q ∼ 1) junction is seen to be reduced by a factor of 300 from that predicted for an undamped junction. The phase is seen to be a good quantum-mechanical variable. The experiments on small capacitance tunnel junctions extend the measurements on the larger-area Josephson junctions from the region in which the phase variable has a fairly well-defined value, i.e. its wavefunction has a narrow width, to the region where its value is almost completely unknown. The charge on the junction becomes well-defined and is predicted to quantize the current through the junction, giving rise to the Coulomb blockade at low bias. I present the first clear observation of the Coulomb blockade in single junctions. The electrical environment of the tunnel junction, however, strongly affects the behavior of the junction: higher resistance leads are observed to greatly sharpen the Coulomb blockade over that seen with lower resistance leads. I present theoretical descriptions of how the environment influences the junctions; comparisons with the experimental results are in reasonable agreement

  20. Earth Pressure on Tunnel Crown

    DEFF Research Database (Denmark)

    Andersen, Lars

    Two different analyses have been carried out in order to find the vertical earth pressure, or overburden pressure, at the crown of a tunnel going through a dike. Firstly, a hand calculation is performed using a simple dispersion of the stresses over depth. Secondly, the finite‐element program...

  1. Introduction to scanning tunneling microscopy

    CERN Document Server

    Chen, C Julian

    2008-01-01

    The scanning tunneling and the atomic force microscope, both capable of imaging individual atoms, were crowned with the Physics Nobel Prize in 1986, and are the cornerstones of nanotechnology today. This is a thoroughly updated version of this 'bible' in the field.

  2. Installation in the SPS tunnel

    CERN Multimedia

    1974-01-01

    The SPS tunnel is 6910 m in circumference and has a cross section of 4 m inner diameter. It is situated at an elevation of 400 m above sea level at a depth below the surface varying between 23 and 65 m. Its walls are lined with a concrete shell of about 30 cm thickness. See also 7410043X

  3. Principles of electron tunneling spectroscopy

    CERN Document Server

    Wolf, E L

    2012-01-01

    Electron tunnelling spectroscopy as a research tool has strongly advanced understanding of superconductivity. This book explains the physics and instrumentation behind the advances illustrated in beautiful images of atoms, rings of atoms and exotic states in high temperature superconductors, and summarizes the state of knowledge that has resulted.

  4. Time tunnels meet warped passages

    CERN Multimedia

    Kushner, David

    2006-01-01

    "Just in time for its 40th anniversary, the classic sci-fi television show "The time tunnel" is out on DVD. The conceit is something every engineer can relate to: a pulled plug. Scientists in an underground lab are working on a secret government experiment in time travel. (1 page)

  5. Zero energy Tunnel-concept

    NARCIS (Netherlands)

    Dzhusupova, R.

    2012-01-01

    Creating a zero energy environment is a hot topic. The developments in this field are based on the concept of the "Trias Energetica": reducing energy consumption, using renewable energy sources, and efficiently using fossil fuels. A zero energy concept can also be applied to road tunnels to improve

  6. Travelling inside the SPS tunnel

    CERN Multimedia

    1974-01-01

    The golf cart proved to be a very useful form of transport around the 7 km circumference of the machine. It could carry four passengers and pull light equipment in its trailer. Here Peter Zettwoch is the driver along a mock-up tunnel for installation tests. (see photo 7401011X and Photo Archive 7401018)

  7. A Seamless Ubiquitous Telehealthcare Tunnel

    Directory of Open Access Journals (Sweden)

    Sao-Jie Chen

    2013-08-01

    Full Text Available Mobile handheld devices are rapidly using to implement healthcare services around the World. Fundamentally, these services utilize telemedicine technologies. A disconnection of a mobile telemedicine system usually results in an interruption, which is embarrassing, and reconnection is necessary during the communication session. In this study, the Stream Control Transmission Protocol (SCTP is adopted to build a stable session tunnel to guarantee seamless switching among heterogeneous wireless communication standards, such as Wi-Fi and 3G. This arrangement means that the telemedicine devices will not be limited by a fixed wireless connection and can switch to a better wireless channel if necessary. The tunnel can transmit plain text, binary data, and video streams. According to the evaluation of the proposed software-based SCTP-Tunnel middleware shown, the performance is lower than anticipated and is slightly slower than a fixed connection. However, the transmission throughput is still acceptable for healthcare professionals in a healthcare enterprise or home care site. It is necessary to build more heterogeneous wireless protocols into the proposed tunnel-switching scheme to support all possible communication protocols. In addition, SCTP is another good choice for promoting communication in telemedicine and healthcare fields.

  8. Tunnel Vision in Environmental Management.

    Science.gov (United States)

    Miller, Alan

    1982-01-01

    Discusses problem-solving styles in environmental management and the specific deficiencies in these styles that might be grouped under the label "tunnel vision," a form of selective attention contributing to inadequate problem-formulation, partial solutions to complex problems, and generation of additional problems. Includes educational…

  9. Management of Carpal Tunnel Syndrome.

    Science.gov (United States)

    Mooar, Pekka A; Doherty, William J; Murray, Jayson N; Pezold, Ryan; Sevarino, Kaitlyn S

    2018-03-15

    The American Academy of Orthopaedic Surgeons (AAOS) has developed Appropriate Use Criteria (AUC) for Management of Carpal Tunnel Syndrome. Evidence-based information, in conjunction with the clinical expertise of physicians, was used to develop the criteria to improve patient care and obtain best outcomes while considering the subtleties and distinctions necessary in making clinical decisions. To provide the evidence foundation for this AUC, the AAOS Evidence-Based Medicine Unit provided the writing panel and voting panel with the 2016 AAOS Clinical Practice Guideline titled Management of Carpal Tunnel Syndrome Evidence-Based Clinical Practice Guideline. The Management of Carpal Tunnel Syndrome AUC clinical patient scenarios were derived from indications typical of patients with suspected carpal tunnel syndrome in clinical practice, as well as from current evidence-based clinical practice guidelines and supporting literature to identify the appropriateness of treatments. The 135 patient scenarios and 6 treatments were developed by the writing panel, a group of clinicians who are specialists in this AUC topic. Next, a separate, multidisciplinary, voting panel (made up of specialists and nonspecialists) rated the appropriateness of treatment of each patient scenario using a 9-point scale to designate a treatment as Appropriate (median rating, 7 to 9), May Be Appropriate (median rating, 4 to 6), or Rarely Appropriate (median rating, 1 to 3).

  10. Tunneling time, what is its meaning?

    International Nuclear Information System (INIS)

    McDonald, C R; Orlando, G; Vampa, G; Brabec, T

    2015-01-01

    The tunnel time ionization dynamics for bound systems in laser fields are investigated. Numerical analysis for a step function switch-on of the field allows for the tunnel time to be defined as the time it takes the ground state to develop the under-barrier wavefunction components necessary to achieve the static field ionization rate. A relation between the tunnel time and the Keldysh time is established. The definition of the tunnel time is extended to time varying fields and experimental possibilities for measuring the tunnel time are discussed

  11. Dirac particle tunneling from black rings

    International Nuclear Information System (INIS)

    Jiang Qingquan

    2008-01-01

    Recent research shows that Hawking radiation can be treated as a quantum tunneling process, and Hawking temperatures of Dirac particles across the horizon of a black hole can be correctly recovered via the fermion tunneling method. In this paper, motivated by the fermion tunneling method, we attempt to apply the analysis to derive Hawking radiation of Dirac particles via tunneling from black ring solutions of 5-dimensional Einstein-Maxwell-dilaton gravity theory. Finally, it is interesting to find that, as in the black hole case, fermion tunneling can also result in correct Hawking temperatures for the rotating neutral, dipole, and charged black rings.

  12. Experimental Evidence for Quantum Tunneling Time

    Science.gov (United States)

    Camus, Nicolas; Yakaboylu, Enderalp; Fechner, Lutz; Klaiber, Michael; Laux, Martin; Mi, Yonghao; Hatsagortsyan, Karen Z.; Pfeifer, Thomas; Keitel, Christoph H.; Moshammer, Robert

    2017-07-01

    The first hundred attoseconds of the electron dynamics during strong field tunneling ionization are investigated. We quantify theoretically how the electron's classical trajectories in the continuum emerge from the tunneling process and test the results with those achieved in parallel from attoclock measurements. An especially high sensitivity on the tunneling barrier is accomplished here by comparing the momentum distributions of two atomic species of slightly deviating atomic potentials (argon and krypton) being ionized under absolutely identical conditions with near-infrared laser pulses (1300 nm). The agreement between experiment and theory provides clear evidence for a nonzero tunneling time delay and a nonvanishing longitudinal momentum of the electron at the "tunnel exit."

  13. Automated Boundary Conditions for Wind Tunnel Simulations

    Science.gov (United States)

    Carlson, Jan-Renee

    2018-01-01

    Computational fluid dynamic (CFD) simulations of models tested in wind tunnels require a high level of fidelity and accuracy particularly for the purposes of CFD validation efforts. Considerable effort is required to ensure the proper characterization of both the physical geometry of the wind tunnel and recreating the correct flow conditions inside the wind tunnel. The typical trial-and-error effort used for determining the boundary condition values for a particular tunnel configuration are time and computer resource intensive. This paper describes a method for calculating and updating the back pressure boundary condition in wind tunnel simulations by using a proportional-integral-derivative controller. The controller methodology and equations are discussed, and simulations using the controller to set a tunnel Mach number in the NASA Langley 14- by 22-Foot Subsonic Tunnel are demonstrated.

  14. Tunneling Flight Time, Chemistry, and Special Relativity.

    Science.gov (United States)

    Petersen, Jakob; Pollak, Eli

    2017-09-07

    Attosecond ionization experiments have not resolved the question "What is the tunneling time?". Different definitions of tunneling time lead to different results. Second, a zero tunneling time for a material particle suggests that the nonrelativistic theory includes speeds greater than the speed of light. Chemical reactions, occurring via tunneling, should then not be considered in terms of a nonrelativistic quantum theory calling into question quantum dynamics computations on tunneling reactions. To answer these questions, we define a new experimentally measurable paradigm, the tunneling flight time, and show that it vanishes for scattering through an Eckart or a square barrier, irrespective of barrier length or height, generalizing the Hartman effect. We explain why this result does not lead to experimental measurement of speeds greater than the speed of light. We show that this tunneling is an incoherent process by comparing a classical Wigner theory with exact quantum mechanical computations.

  15. Macroscopic quantum tunneling in Josephson tunnel junctions and Coulomb blockade in single small tunnel junctions

    International Nuclear Information System (INIS)

    Cleland, A.N.

    1991-01-01

    Experiments investigated the process of macroscopic quantum tunneling in a moderately-damped, resistively shunted, Josephson junction are described, followed by a discussion of experiments performed on very-small-capacitance normal-metal tunnel junctions. The experiments on the resistively-shunted Josephson junction were designed to investigate a quantum process, that of the tunneling of the Josephson-phase variable under a potential barrier, in a system in which dissipation plays a major role in the dynamics of motion. All the parameters of the junction were measured using the classical phenomena of thermal activation and resonant activation. Theoretical predictions are compared with the experimental results, showing good agreement with no adjustable parameters. The experiments on small-capacitance tunnel junctions extend the measurements on the large-area Josephson junctions from the region in which the phase variable has a fairly well-defined value, i.e. its wave function has a narrow width, to the region where its value is almost completely unknown. The charge on the junction becomes well-defined and is predicted to quantize the current through the junction, giving rise to the Coulomb blockade at low bias

  16. Resonant tunnel magnetoresistance in a double magnetic tunnel junction

    KAUST Repository

    Useinov, Arthur

    2011-08-09

    We present quasi-classical approach to calculate a spin-dependent current and tunnel magnetoresistance (TMR) in double magnetic tunnel junctions (DMTJ) FML/I/FMW/I/FMR, where the magnetization of the middle ferromagnetic metal layer FMW can be aligned parallel or antiparallel with respect to the fixed magnetizations of the left FML and right FMR ferromagnetic electrodes. The transmission coefficients for components of the spin-dependent current, and TMR are calculated as a function of the applied voltage. As a result, we found a high resonant TMR. Thus, DMTJ can serve as highly effective magnetic nanosensor for biological applications, or as magnetic memory cells by switching the magnetization of the inner ferromagnetic layer FMW.© Springer Science+Business Media, LLC 2011.

  17. The Third Quantization: To Tunnel or Not to Tunnel?

    Directory of Open Access Journals (Sweden)

    Mariam Bouhmadi-López

    2018-02-01

    Full Text Available Within the framework of the third quantization, we consider the possibility that an initially recollapsing baby universe can enter a stage of near de Sitter inflation by tunnelling through a Euclidean wormhole that connects the recollapsing and inflationary geometries. We present the solutions for the evolution of the scale factor in the Lorentzian and Euclidean regions as well as the probability that the baby universe indeed crosses the wormhole when it reaches its maximum size.

  18. Klein tunneling phenomenon with pair creation process

    Science.gov (United States)

    Wu, G. Z.; Zhou, C. T.; Fu, L. B.

    2018-01-01

    In this paper, we study the Klein tunneling phenomenon with electron-positron pair creation process. Pairs can be created from the vacuum by a supercritical single-well potential (for electrons). In the time region, the time-dependent growth pattern of the created pairs can be characterized by four distinct regimes which can be considered as four different statuses of the single well. We find that if positrons penetrate the single well by Klein tunneling in different statuses, the total number of the tunneling positrons will be different. If Klein tunneling begins at the initial stage of the first status i.e. when the sing well is empty, the tunneling process and the total number of tunneling positrons are similar to the traditional Klein tunneling case without considering the pair creation process. As the tunneling begins later, the total tunneling positron number increases. The number will finally settle to an asymptotic value when the tunneling begins later than the settling-down time t s of the single well which has been defined in this paper.

  19. Seismic scanning tunneling macroscope - Theory

    KAUST Repository

    Schuster, Gerard T.

    2012-09-01

    We propose a seismic scanning tunneling macroscope (SSTM) that can detect the presence of sub-wavelength scatterers in the near-field of either the source or the receivers. Analytic formulas for the time reverse mirror (TRM) profile associated with a single scatterer model show that the spatial resolution limit to be, unlike the Abbe limit of λ/2, independent of wavelength and linearly proportional to the source-scatterer separation as long as the point scatterer is in the near-field region; if the sub-wavelength scatterer is a spherical impedance discontinuity then the resolution will also be limited by the radius of the sphere. Therefore, superresolution imaging can be achieved as the scatterer approaches the source. This is analogous to an optical scanning tunneling microscope that has sub-wavelength resolution. Scaled to seismic frequencies, it is theoretically possible to extract 100 Hz information from 20 Hz data by imaging of near-field seismic energy.

  20. Single-contact tunneling thermometry

    Science.gov (United States)

    Maksymovych, Petro

    2016-02-23

    A single-contact tunneling thermometry circuit includes a tunnel junction formed between two objects. Junction temperature gradient information is determined based on a mathematical relationship between a target alternating voltage applied across the junction and the junction temperature gradient. Total voltage measured across the junction indicates the magnitude of the target alternating voltage. A thermal gradient is induced across the junction. A reference thermovoltage is measured when zero alternating voltage is applied across the junction. An increasing alternating voltage is applied while measuring a thermovoltage component and a DC rectification voltage component created by the applied alternating voltage. The target alternating voltage is reached when the thermovoltage is nullified or doubled by the DC rectification voltage depending on the sign of the reference thermovoltage. Thermoelectric current and current measurements may be utilized in place of the thermovoltage and voltage measurements. The system may be automated with a feedback loop.

  1. Spin tunneling in magnetic molecules

    Science.gov (United States)

    Kececioglu, Ersin

    In this thesis, we will focus on spin tunneling in a family of systems called magnetic molecules such as Fe8 and Mn12. This is comparatively new, in relation to other tunneling problems. Many issues are not completely solved and/or understood yet. The magnetic molecule Fe 8 has been observed to have a rich pattern of degeneracies in its magnetic spectrum. We focus on these degeneracies from several points of view. We start with the simplest anisotropy Hamiltonian to describe the Fe 8 molecule and extend our discussion to include higher order anisotropy terms. We give analytical expressions as much as we can, for the degeneracies in the semi-classical limit in both cases. We reintroduce jump instantons to the instanton formalism. Finally, we discuss the effect of the environment on the molecule. Our results, for all different models and techniques, agree well with both experimental and numerical results.

  2. Tunneling magnetoresistance in Si nanowires

    KAUST Repository

    Montes Muñoz, Enrique

    2016-11-09

    We investigate the tunneling magnetoresistance of small diameter semiconducting Si nanowires attached to ferromagnetic Fe electrodes, using first principles density functional theory combined with the non-equilibrium Green\\'s functions method for quantum transport. Silicon nanowires represent an interesting platform for spin devices. They are compatible with mature silicon technology and their intrinsic electronic properties can be controlled by modifying the diameter and length. Here we systematically study the spin transport properties for neutral nanowires and both n and p doping conditions. We find a substantial low bias magnetoresistance for the neutral case, which halves for an applied voltage of about 0.35 V and persists up to 1 V. Doping in general decreases the magnetoresistance, as soon as the conductance is no longer dominated by tunneling.

  3. Underwater piercing of a tunnel

    Energy Technology Data Exchange (ETDEWEB)

    Solvik, O.

    1984-11-01

    Norwegian consultants and contractors have been confronted with the task of blasting a final penetrating passage that will open the way for the water in a reservoir to flow through the hydropower turbines. Norway has almost certainly led in this area because of its special topographical and geological conditions. The glacial activities have created a number of natural and very deep lakes forming cheap reservoirs. Piercings at depths up to about 100 m have been performed. Problems tend to increase with depth, but unsuccessful penetration can occur at any depth. Secondary effects to consider include the danger of slides when the water level is lowered, wave erosion along the lowered new shoreline, erosion at all streams and rivers flowing into the lake and groundwater erosion in the newly exposed dry shoreline. Methods of penetration can be roughly divided into two categories: penetration against the open tunnel shaft (open system); and penetration against the closed tunnel shaft (closed system). 6 figures.

  4. Seismic scanning tunneling macroscope - Theory

    KAUST Repository

    Schuster, Gerard T.; Hanafy, Sherif M.; Huang, Yunsong

    2012-01-01

    We propose a seismic scanning tunneling macroscope (SSTM) that can detect the presence of sub-wavelength scatterers in the near-field of either the source or the receivers. Analytic formulas for the time reverse mirror (TRM) profile associated with a single scatterer model show that the spatial resolution limit to be, unlike the Abbe limit of λ/2, independent of wavelength and linearly proportional to the source-scatterer separation as long as the point scatterer is in the near-field region; if the sub-wavelength scatterer is a spherical impedance discontinuity then the resolution will also be limited by the radius of the sphere. Therefore, superresolution imaging can be achieved as the scatterer approaches the source. This is analogous to an optical scanning tunneling microscope that has sub-wavelength resolution. Scaled to seismic frequencies, it is theoretically possible to extract 100 Hz information from 20 Hz data by imaging of near-field seismic energy.

  5. Tunneling of a coupled system

    International Nuclear Information System (INIS)

    Avishai, Y.

    1985-01-01

    We consider tunneling through a potential barrier V(x) in the presence of a coupling term W(x,y). Let H(y) be the internal Hamiltonian associated with the coordinate y and let E 0 (x) be the ground state energy of the operator H(x;y) = H(y) + W(x,y) in which x is a parameter. Our result for the tunneling probability (in the WKB approximation) is P = exp(2i ∫ k 0 (x)dx) where, at energy E, k 0 (x) = [E-E 0 (x)-V(x)]sup(1/2)/(h/2π) is the local wave number in the presence of coupling. (orig.)

  6. Seismic prediction ahead of tunnel constructions

    Science.gov (United States)

    Jetschny, S.; Bohlen, T.; Nil, D. D.; Giese, R.

    2007-12-01

    To increase safety and efficiency of tunnel constructions, online seismic exploration ahead of a tunnel can become a valuable tool. Within the \\it OnSite project founded by the BMBF (German Ministry of Education and Research) within \\it GeoTechnologien a new forward looking seismic imaging technique is developed to e.g. determine weak and water bearing zones ahead of the constructions. Our approach is based on the excitation and registration of \\it tunnel surface waves. These waves are excited at the tunnel face behind the cutter head of a tunnel boring machine and travel into drilling direction. Arriving at the front face they generate body waves (mainly S-waves) propagating further ahead. Reflected S-waves are back- converted into tunnel surface waves. For a theoretical description of the conversion process and for finding optimal acquisition geometries it is of importance to study the propagation characteristics of tunnel surface waves. 3D seismic finite difference modeling and analytic solutions of the wave equation in cylindric coordinates revealed that at higher frequencies, i.e. if the tunnel diameter is significantly larger than the wavelength of S-waves, these surface waves can be regarded as Rayleigh-waves circulating the tunnel. For smaller frequencies, i.e. when the S-wavelength approaches the tunnel diameter, the propagation characteristics of these surface waves are then similar to S- waves. Field measurements performed by the GeoForschungsZentrum Potsdam, Germany at the Gotthard Base Tunnel (Switzerland) show both effects, i.e. the propagation of Rayleigh- and body-wave like waves along the tunnel. To enhance our understanding of the excitation and propagation characteristics of tunnel surface waves the transition of Rayleigh to tube-waves waves is investigated both analytically and by numerical simulations.

  7. Digging the CNGS decay tunnel

    CERN Multimedia

    Patrice Loiez

    2002-01-01

    Products of the collision between a proton beam and a graphite target will pass through a horn containing an electric field that will produce a focused beam. These particles will decay into muon neutrinos within the tunnel that is being constructed in these images. The neutrinos will then travel 730 km to Gran Sasso in Italy where huge detectors will observe the beam to study a process called neutrino oscillation.

  8. Dissipative Effect and Tunneling Time

    Directory of Open Access Journals (Sweden)

    Samyadeb Bhattacharya

    2011-01-01

    Full Text Available The quantum Langevin equation has been studied for dissipative system using the approach of Ford et al. Here, we have considered the inverted harmonic oscillator potential and calculated the effect of dissipation on tunneling time, group delay, and the self-interference term. A critical value of the friction coefficient has been determined for which the self-interference term vanishes. This approach sheds new light on understanding the ion transport at nanoscale.

  9. Variability in ACL tunnel placement: observational clinical study of surgeon ACL tunnel variability.

    Science.gov (United States)

    Wolf, Brian R; Ramme, Austin J; Wright, Rick W; Brophy, Robert H; McCarty, Eric C; Vidal, Armando R; Parker, Richard D; Andrish, Jack T; Amendola, Annunziato

    2013-06-01

    Multicenter and multisurgeon cohort studies on anterior cruciate ligament (ACL) reconstruction are becoming more common. Minimal information exists on intersurgeon and intrasurgeon variability in ACL tunnel placement. Purpose/ The purpose of this study was to analyze intersurgeon and intrasurgeon variability in ACL tunnel placement in a series of The Multicenter Orthopaedic Outcomes Network (MOON) ACL reconstruction patients and in a clinical cohort of ACL reconstruction patients. The hypothesis was that there would be minimal variability between surgeons in ACL tunnel placement. Cross-sectional study; Level of evidence, 3. Seventy-eight patients who underwent ACL reconstruction by 8 surgeons had postoperative imaging with computed tomography, and ACL tunnel location and angulation were analyzed using 3-dimensional surface processing and measurement. Intersurgeon and intrasurgeon variability in ACL tunnel placement was analyzed. For intersurgeon variability, the range in mean ACL femoral tunnel depth between surgeons was 22%. For femoral tunnel height, there was a 19% range. Tibial tunnel location from anterior to posterior on the plateau had a 16% range in mean results. There was only a small range of 4% for mean tibial tunnel location from the medial to lateral dimension. For intrasurgeon variability, femoral tunnel depth demonstrated the largest ranges, and tibial tunnel location from medial to lateral on the plateau demonstrated the least variability. Overall, surgeons were relatively consistent within their own cases. Using applied measurement criteria, 85% of femoral tunnels and 90% of tibial tunnels fell within applied literature-based guidelines. Ninety-one percent of the axes of the femoral tunnels fell within the boundaries of the femoral footprint. The data demonstrate that surgeons performing ACL reconstructions are relatively consistent between each other. There is, however, variability of average tunnel placement up to 22% of mean condylar depth

  10. Tunneling beyond the Fermilab site

    International Nuclear Information System (INIS)

    Baker, S.; Elwyn, A.; Lach, J.; Read, A.

    1983-01-01

    An accelerator that crosses the Fermilab site boundary must have a minimum effect on the surrounding environment and the people residing in the area. Unobstructed public access should be allowed above the ring except in relatively few areas such as the injection, dump, and experimental regions. The accelerator should be a benign and unobtrusive neighbor not only when it is completed but also in the construction period. For these reasons underground tunneling for all or most of the ring seems attractive. In this note we look into some questions raised by tunneling beyond the Fermilab site. Most of our discussion is of general applicability. However, we will use as examples two specific ring configurations. The examples have not been optimized from the point of view of physics output or accelerator technology but are just specific examples which allow us to study questions of tunneling. One is a ring of 5 km radius (5 TeV) tangent to the Tevatron and entirely east of the Fox River and fed by a beam from the Tevatron which crosses under the river. We assume that each of these machines will have 100 beam fills per year and we scale the maximum intensities with the accelerator radii. Thus we assume that there will be 1.0 E14 protons in each beam of the 20 TeV machine and 2.5 E13 for the 5 TeV machine

  11. New vision of magnetic tunnelling

    Energy Technology Data Exchange (ETDEWEB)

    Friedman, Jonathan R. [Amherst College, Amhurst, MA (United States)

    2002-01-01

    Recent experiments support the idea that crystal defects may be responsible for the quantum tunnelling of magnetic moments in molecular magnets at low temperatures. The magnetic moment of a typical bar magnet will never spontaneously reverse direction. However, thermal fluctuations can flip the moment of a magnetic particle just a few nanometres across. The particle can be cooled to nearly absolute zero to suppress this process, but the moment may still find a way to reverse via quantum tunnelling. Quantum tunnelling of magnetization has been the subject of decades of research. Until a few years ago, however, there had only been circumstantial evidence for the phenomenon. This is because most systems of small magnetic particles are hard to characterize - the particles have a variety of shapes, sizes and other properties, making it difficult to compare data with theory. Some real progress was made a few years ago through research into high-spin single-molecule magnets. With dimensions of about a nanometre, these magnets are usually composed of a magnetic core that is surrounded by organic complexes. When they crystallize into a regular lattice, the organic ions keep neighbouring magnets well separated so that they interact only weakly. Ideally all the molecules are identical because they have been built chemically, which means that they can be characterized precisely and that any data can be analysed quantitatively. The most studied of these molecules is manganese-12 acetate (Mn{sub 12}). Within each molecule, the spins of the eight Mn{sup 3+} ions (each with S=2) are antiparallel to the spins of the four Mn{sup 4+} ions (each with S=3/2), giving Mn{sub 12} a total spin of S=10. Or, to put it another way, the magnetic moment of Mn{sub 12} is 20 times larger than that of the electron. Now Eugene Chudnovsky of Lehman College in New York and Dmitry Garanin of the University of Mainz in Germany have suggested a new mechanism for producing tunnelling in Mn{sub 12

  12. Chaos regularization of quantum tunneling rates

    International Nuclear Information System (INIS)

    Pecora, Louis M.; Wu Dongho; Lee, Hoshik; Antonsen, Thomas; Lee, Ming-Jer; Ott, Edward

    2011-01-01

    Quantum tunneling rates through a barrier separating two-dimensional, symmetric, double-well potentials are shown to depend on the classical dynamics of the billiard trajectories in each well and, hence, on the shape of the wells. For shapes that lead to regular (integrable) classical dynamics the tunneling rates fluctuate greatly with eigenenergies of the states sometimes by over two orders of magnitude. Contrarily, shapes that lead to completely chaotic trajectories lead to tunneling rates whose fluctuations are greatly reduced, a phenomenon we call regularization of tunneling rates. We show that a random-plane-wave theory of tunneling accounts for the mean tunneling rates and the small fluctuation variances for the chaotic systems.

  13. Fiber coupled ultrafast scanning tunneling microscope

    DEFF Research Database (Denmark)

    Keil, Ulrich Dieter Felix; Jensen, Jacob Riis; Hvam, Jørn Märcher

    1997-01-01

    We report on a scanning tunneling microscope with a photoconductive gate in the tunneling current circuit. The tunneling tip is attached to a coplanar transmission line with an integrated photoconductive switch. The switch is illuminated through a fiber which is rigidly attached to the switch...... waveguide. The measurements show that the probe works as a transient voltage detector in contact and a capacitively coupled transient field detector in tunneling mode. We do not measure the transient voltage change in the ohmic tunneling current. In this sense, the spatial resolution for propagating...... substrate. By using a firmly attached fiber we achieve an excellent reproducibility and unconstrained positioning of the tip. We observe a transient signal with 2.9 ps pulse width in tunneling mode and 5 ps in contact mode. The instrument is applied to investigating the mode structure on a coplanar...

  14. In-mine (tunnel-to-tunnel) electrical resistance tomography in South African platinum mines

    CSIR Research Space (South Africa)

    Van Schoor, Abraham M

    2009-12-01

    Full Text Available The applicability of tunnel-to-tunnel electrical resistance tomography (ERT) for imaging disruptive geological structures ahead of mining, in an igneous platinum mining environment is assessed. The geophysical targets of interest are slump...

  15. Tunneling anisotropic magnetoresistance in Co/AIOx/Al tunnel junctions with fcc Co (111) electrodes

    NARCIS (Netherlands)

    Wang, Kai; Tran, T. Lan Ahn; Brinks, Peter; Brinks, P.; Sanderink, Johannes G.M.; Bolhuis, Thijs; van der Wiel, Wilfred Gerard; de Jong, Machiel Pieter

    2013-01-01

    Tunneling anisotropic magnetoresistance (TAMR) has been characterized in junctions comprised of face-centered cubic (fcc) Co (111) ferromagnetic electrodes grown epitaxially on sapphire substrates, amorphous AlOx tunnel barriers, and nonmagnetic Al counterelectrodes. Large TAMR ratios have been

  16. RITD – Wind tunnel testing

    Science.gov (United States)

    Haukka, Harri; Harri, Ari-Matti; Aleksashkin, Sergei; Koryanov, Valeri; Schmidt, Walter; Heilimo, Jyri; Finchenko, Valeri; Martynov, Maxim; Ponomarenko, Andrey; Kazakovtsev, Victor; Arruego, Ignazio

    2015-04-01

    An atmospheric re-entry and descent and landing system (EDLS) concept based on inflatable hypersonic decelerator techniques is highly promising for the Earth re-entry missions. We developed such EDLS for the Earth re-entry utilizing a concept that was originally developed for Mars. This EU-funded project is called RITD - Re-entry: Inflatable Technology Development - and it was to assess the bene¬fits of this technology when deploying small payloads from low Earth orbits to the surface of the Earth with modest costs. The principal goal was to assess and develope a preliminary EDLS design for the entire relevant range of aerodynamic regimes expected to be encountered in Earth's atmosphere during entry, descent and landing. The RITD entry and descent system utilizes an inflatable hypersonic decelerator. Development of such system requires a combination of wind tunnel tests and numerical simulations. This included wind tunnel tests both in transsonic and subsonic regimes. The principal aim of the wind tunnel tests was the determination of the RITD damping factors in the Earth atmosphere and recalculation of the results for the case of the vehicle descent in the Mars atmosphere. The RITD mock-up model used in the tests was in scale of 1:15 of the real-size vehicle as the dimensions were (midsection) diameter of 74.2 mm and length of 42 mm. For wind tunnel testing purposes the frontal part of the mock-up model body was manufactured by using a PolyJet 3D printing technology based on the light curing of liquid resin. The tail part of the mock-up model body was manufactured of M1 grade copper. The structure of the mock-up model placed th center of gravity in the same position as that of the real-size RITD. The wind tunnel test program included the defining of the damping factor at seven values of Mach numbers 0.85; 0.95; 1.10; 1.20; 1.25; 1.30 and 1.55 with the angle of attack ranging from 0 degree to 40 degrees with the step of 5 degrees. The damping characteristics of

  17. PUREX Storage Tunnels dangerous waste permit application

    International Nuclear Information System (INIS)

    1991-12-01

    This report is part of a dangerous waste permit application for the storage of wastes from the Purex process at Hanford. Appendices are presented on the following: construction drawings; HSW-5638, specifications for disposal facility for failed equipment, Project CA-1513-A; HWS-8262, specification for Purex equipment disposal, Project CGC 964; storage tunnel checklist; classification of residual tank heels in Purex storage tunnels; emergency plan for Purex facility; training course descriptions; and the Purex storage tunnels engineering study

  18. MISTY ECHO tunnel dynamics experiment data report

    International Nuclear Information System (INIS)

    Phillips, J.S.; Luke, B.A.; Long, J.W.; Lee, J.G.

    1992-04-01

    Tunnel damage resulting from seismic loading is an important issue for the Yucca Mountain nuclear waste repository. The tunnel dynamics experiment was designed to obtain and document ground motions, permanent displacements, observable changes in fracture patterns, and visible damage at ground motion levels of interest to the Yucca Mountain Project. Even though the maximum free-field loading on this tunnel was 28 g, the damage observed was minor. Fielding details, data obtained, and supporting documentation are reported

  19. Theoretical approach to the scanning tunneling microscope

    International Nuclear Information System (INIS)

    Noguera, C.

    1990-01-01

    Within a one-electron approach, based on a Green's-function formalism, a nonperturbative expression for the tunneling current is obtained and used to discuss which spectroscopic information may be deduced from a scanning-tunneling-microscope experiment. It is shown up to which limits the voltage dependence of the tunneling current reproduces the local density of states at the surface, and how the reflection coefficients of the electronic waves at the surface may modify it

  20. Quantum tunneling and field electron emission theories

    CERN Document Server

    Liang, Shi-Dong

    2013-01-01

    Quantum tunneling is an essential issue in quantum physics. Especially, the rapid development of nanotechnology in recent years promises a lot of applications in condensed matter physics, surface science and nanodevices, which are growing interests in fundamental issues, computational techniques and potential applications of quantum tunneling. The book involves two relevant topics. One is quantum tunneling theory in condensed matter physics, including the basic concepts and methods, especially for recent developments in mesoscopic physics and computational formulation. The second part is the f

  1. Energy Efficiency of Tunnel Boring Machines.

    OpenAIRE

    Grishenko, Vitaly

    2014-01-01

    Herrenknecht AG is a German world-leading Tunnel Boring Machines manufacturer showing strong awareness and concern regarding environmental issues. The company supports research on the Energy Efficiency (EE) of their products, aimed at the development of intelligent design for a green Tunnel Boring Machine. The aim of this project is to produce a ’status quo’ report on EE of three types of Tunnel Boring Machines (Hardrock, EPB and Mixshield TBM). In the framework of this research 39 projects a...

  2. Climatic wind tunnel for wind engineering tasks

    Czech Academy of Sciences Publication Activity Database

    Kuznetsov, Sergeii; Pospíšil, Stanislav; Král, Radomil

    2015-01-01

    Roč. 112, 2-B (2015), s. 303-316 ISSN 1897-628X R&D Projects: GA ČR(CZ) GA14-12892S Keywords : climatic tunnel * wind tunnel * atmospheric boundary layer * flow resistance * wind tunnel contraction Subject RIV: JM - Building Engineering https://suw.biblos.pk.edu.pl/resources/i5/i6/i6/i7/i6/r56676/KuznetsovS_ClimaticWind.pdf

  3. Nuclear fission as a macroscopic quantum tunneling

    International Nuclear Information System (INIS)

    Takigawa, N.

    1995-01-01

    We discuss nuclear fission from the point of view of a macroscopic quantum tunneling, one of whose major interests is to study the effects of environments on the tunneling rate of a macroscopic variable. We show that a vibrational excitation of the fissioning nucleus significantly enhances the fission rate. We show this effect by two different methods. The one is to treat the vibrational excitation as an environmental degree of freedom, the other treats the fission as a two dimensional quantum tunneling. (author)

  4. Femtosecond tunneling response of surface plasmon polaritons

    DEFF Research Database (Denmark)

    Keil, Ulrich Dieter Felix; Ha, Taekjip; Jensen, Jacob Riis

    1998-01-01

    We obtain femtosecond (200 fs) time resolution using a scanning tunneling microscope on surface plasmon polaritons (SPPs) generated by two 100 fs laser beams in total internal reflection geometry. The tunneling gap dependence of the signal clearly indicates the tunneling origin of the signal...... and suggests that nanometer spatial resolution can be obtained together with femtosecond temporal resolution. This fast response, in contrast to the picosecond decay time of SPPs revealed by differential reflectivity measurements, can be attributed to a coherent superposition of SPPs rectified at the tunneling...

  5. PUREX Storage Tunnels dangerous waste permit application

    International Nuclear Information System (INIS)

    1991-12-01

    The PUREX Storage Tunnels are a mixed waste storage unit consisting of two underground railroad tunnels: Tunnel Number 1 designated 218-E-14 and Tunnel Number 2 designated 218-E-15. The two tunnels are connected by rail to the PUREX Plant and combine to provide storage space for 48 railroad cars (railcars). The PUREX Storage Tunnels provide a long-term storage location for equipment removed from the PUREX Plant. Transfers into the PUREX Storage Tunnels are made on an as-needed basis. Radioactively contaminated equipment is loaded on railcars and remotely transferred by rail into the PUREX Storage Tunnels. Railcars act as both a transport means and a storage platform for equipment placed into the tunnels. This report consists of part A and part B. Part A reports on amounts and locations of the mixed water. Part B permit application consists of the following: Facility Description and General Provisions; Waste Characteristics; Process Information; Groundwater Monitoring; Procedures to Prevent Hazards; Contingency Plan; Personnel Training; Exposure Information Report

  6. Enhanced MRI in carpal tunnel syndrome

    International Nuclear Information System (INIS)

    Hayakawa, Katsuhiko; Nakane, Takashi; Kobayashi, Shigeru; Asai, Takahiro; Wada, Kunio; Yoshizawa, Hidezo

    1998-01-01

    In this study, we performed contrast-enhanced MRI in patients with idiopathic carpal tunnel syndrome and examined the morphologic change in the carpal tunnel. In the transverse section of the opening of carpal tunnel where scaphoid and pisiform bones are figured out, we measured and examined 4 items, viz. the soft carpal tunnel volume, flat rate of median nerve, position of median nerve and thickness of palmer ligaments composing the base of carpal tunnel, with an image analyzer attached to the MRI apparatus. Whereas the average carpal tunnel volume in 12 hands of normal controls was 166.8 mm 2 , that in 74 hands of carpal tunnel syndrome was 207.2 mm 2 , a significant increase compared with the normal controls. The flat rate of median nerve was 46% in the controls, but that was 37.5% in the carpal tunnel syndrome, a significant flattening was noted. We connected the peaks of the scaphoid node and pisiform bone with a line and named it standard line. When we observed the position of median nerve in the carpal tunnel, the nerve in 9 of 12 hands, 75%, lay below the standard line in the controls, but the nerve in 65 of 74 hands, 87.8%, lay above the standard line in the carpal tunnel syndrome, clearly showing that the median nerve had shifted to the palmar side. Regarding these morphologic changes of the carpal tunnel, the internal pressure of the carpal tunnel is considered to be raised with swelling of the soft tissues mainly composing the inside of carpal tunnel, thus the area of cross section of carpal tunnel to be increased, the median nerve to be shifted to the palmar side and the median nerve to be compressed by the transverse carpal ligament at that time. Although we can observe these morphological changes readily in MRI images, these images show only the results of carpal tunnel syndrome after all, and do not specify the direct causes. However, we believe that these facts are important factors in the manifestation of idiopathic carpal tunnel syndrome. (author)

  7. Relativistic tunneling through two successive barriers

    International Nuclear Information System (INIS)

    Lunardi, Jose T.; Manzoni, Luiz A.

    2007-01-01

    We study the relativistic quantum mechanical problem of a Dirac particle tunneling through two successive electrostatic barriers. Our aim is to study the emergence of the so-called generalized Hartman effect, an effect observed in the context of nonrelativistic tunneling as well as in its counterparts and which is often associated with the possibility of superluminal velocities in the tunneling process. We discuss the behavior of both the phase (or group) tunneling time and the dwell time, and show that in the limit of opaque barriers the relativistic theory also allows the emergence of the generalized Hartman effect. We compare our results with the nonrelativistic ones and discuss their interpretation

  8. Tunnelling in Dante's Inferno

    Energy Technology Data Exchange (ETDEWEB)

    Furuuchi, Kazuyuki [Manipal Centre for Natural Sciences, Manipal University, Dr.T.M.A. Pai Planetarium Building, Madhav Nagar, Manipal, Karnataka 576104 (India); Sperling, Marcus, E-mail: kazuyuki.furuuchi@manipal.edu, E-mail: marcus.sperling@univie.ac.at [Fakultät für Physik, Universität Wien, Boltzmanngasse 5, A-1090 Wien (Austria)

    2017-05-01

    We study quantum tunnelling in Dante's Inferno model of large field inflation. Such a tunnelling process, which will terminate inflation, becomes problematic if the tunnelling rate is rapid compared to the Hubble time scale at the time of inflation. Consequently, we constrain the parameter space of Dante's Inferno model by demanding a suppressed tunnelling rate during inflation. The constraints are derived and explicit numerical bounds are provided for representative examples. Our considerations are at the level of an effective field theory; hence, the presented constraints have to hold regardless of any UV completion.

  9. Tunneling with dissipation in open quantum systems

    International Nuclear Information System (INIS)

    Adamyan, G.G.; Antonenko, N.V.; Scheid, W.

    1997-01-01

    Based on the general form of the master equation for open quantum systems the tunneling is considered. Using the path integral technique a simple closed form expression for the tunneling rate through a parabolic barrier is obtained. The tunneling in the open quantum systems strongly depends on the coupling with environment. We found the cases when the dissipation prohibits tunneling through the barrier but decreases the crossing of the barrier for the energies above the barrier. As a particular application, the case of decay from the metastable state is considered

  10. Fire safety assessment of tunnel structures

    DEFF Research Database (Denmark)

    Gkoumas, Konstantinos; Giuliani, Luisa; Petrini, Francesco

    2011-01-01

    .g. structural and non structural, organizational, human behavior). This is even more truth for the fire safety design of such structures. Fire safety in tunnels is challenging because of the particular environment, bearing in mind also that a fire can occur in different phases of the tunnel’s lifecycle. Plans...... for upgrading fire safety provisions and tunnel management are also important for existing tunnels. In this study, following a brief introduction of issues regarding the above mentioned aspects, the structural performance of a steel rib for a tunnel infrastructure subject to fire is assessed by means...

  11. Resonant tunneling of electrons in quantum wires

    International Nuclear Information System (INIS)

    Krive, I.V.; Shekhter, R.I.; Jonson, M.; Krive, I.V.

    2010-01-01

    We considered resonant electron tunneling in various nanostructures including single wall carbon nanotubes, molecular transistors and quantum wires formed in two-dimensional electron gas. The review starts with a textbook description of resonant tunneling of noninteracting electrons through a double-barrier structure. The effects of electron-electron interaction in sequential and resonant electron tunneling are studied by using Luttinger liquid model of electron transport in quantum wires. The experimental aspects of the problem (fabrication of quantum wires and transport measurements) are also considered. The influence of vibrational and electromechanical effects on resonant electron tunneling in molecular transistors is discussed.

  12. Tunnelling in Dante's Inferno

    International Nuclear Information System (INIS)

    Furuuchi, Kazuyuki; Sperling, Marcus

    2017-01-01

    We study quantum tunnelling in Dante's Inferno model of large field inflation. Such a tunnelling process, which will terminate inflation, becomes problematic if the tunnelling rate is rapid compared to the Hubble time scale at the time of inflation. Consequently, we constrain the parameter space of Dante's Inferno model by demanding a suppressed tunnelling rate during inflation. The constraints are derived and explicit numerical bounds are provided for representative examples. Our considerations are at the level of an effective field theory; hence, the presented constraints have to hold regardless of any UV completion.

  13. Electronic tunneling currents at optical frequencies

    Science.gov (United States)

    Faris, S. M.; Fan, B.; Gustafson, T. K.

    1975-01-01

    Rectification characteristics of nonsuperconducting metal-barrier-metal junctions as deduced from electronic tunneling theory have been observed experimentally for optical frequency irradiation of the junction.

  14. Lowest order in inelastic tunneling approximation : efficient scheme for simulation of inelastic electron tunneling data

    NARCIS (Netherlands)

    Rossen, E.T.R.; Flipse, C.F.J.; Cerda, J.I.

    2013-01-01

    We have developed an efficient and accurate formalism which allows the simulation at the ab initio level of inelastic electron tunneling spectroscopy data under a scanning tunneling microscope setup. It exploits fully the tunneling regime by carrying out the structural optimization and vibrational

  15. Probing spin-polarized tunneling at high bias and temperature with a magnetic tunnel transistor

    NARCIS (Netherlands)

    Park, B.G.; Banerjee, T.; Min, B.C.; Sanderink, Johannes G.M.; Lodder, J.C.; Jansen, R.

    2005-01-01

    The magnetic tunnel transistor (MTT) is a three terminal hybrid device that consists of a tunnel emitter, a ferromagnetic (FM) base, and a semiconductor collector. In the MTT with a FM emitter and a single FM base, spin-polarized hot electrons are injected into the base by tunneling. After

  16. Resonant tunneling via spin-polarized barrier states in a magnetic tunnel junction

    NARCIS (Netherlands)

    Jansen, R.; Lodder, J.C.

    2000-01-01

    Resonant tunneling through states in the barrier of a magnetic tunnel junction has been analyzed theoretically for the case of a spin-polarized density of barrier states. It is shown that for highly spin-polarized barrier states, the magnetoresistance due to resonant tunneling is enhanced compared

  17. Percutaneous Creation of Bare Intervascular Tunnels for Salvage of Thrombosed Hemodialysis Fistulas Without Recanalizable Outflow

    International Nuclear Information System (INIS)

    Chen, Matt Chiung-Yu; Wang, Yen-Chi; Weng, Mei-Jui

    2015-01-01

    PurposeThis study aimed to retrospectively assess the efficacy of a bare intervascular tunnel for salvage of a thrombosed hemodialysis fistula. We examined the clinical outcomes and provided follow-up images of the bare intervascular tunnel.Materials and MethodsEight thrombosed fistulas lacked available recanalizable outflow veins were included in this study. These fistulas were salvaged by re-directing access site flow to a new outflow vein through a percutaneously created intervascular tunnel without stent graft placement. The post-intervention primary and secondary access patency rates were calculated using the Kaplan–Meier method.ResultsThe procedural and clinical success rates were 100 %. Post-intervention primary and secondary access patency at 300 days were 18.7 ± 15.8 and 87.5 ± 11.7 %, respectively. The mean follow-up period was 218.7 days (range 10–368 days). One patient died of acute myocardial infarction 10 days after the procedure. No other major complications were observed. Minor complications, such as swelling, ecchymosis, and pain around the tunnel, occurred in all of the patients.ConclusionsPercutaneous creation of a bare intervascular tunnel is a treatment option for thrombosed hemodialysis fistulas without recanalizable outflow in selected patients

  18. Giant electrode effect on tunnelling electroresistance in ferroelectric tunnel junctions.

    Science.gov (United States)

    Soni, Rohit; Petraru, Adrian; Meuffels, Paul; Vavra, Ondrej; Ziegler, Martin; Kim, Seong Keun; Jeong, Doo Seok; Pertsev, Nikolay A; Kohlstedt, Hermann

    2014-11-17

    Among recently discovered ferroelectricity-related phenomena, the tunnelling electroresistance (TER) effect in ferroelectric tunnel junctions (FTJs) has been attracting rapidly increasing attention owing to the emerging possibilities of non-volatile memory, logic and neuromorphic computing applications of these quantum nanostructures. Despite recent advances in experimental and theoretical studies of FTJs, many questions concerning their electrical behaviour still remain open. In particular, the role of ferroelectric/electrode interfaces and the separation of the ferroelectric-driven TER effect from electrochemical ('redox'-based) resistance-switching effects have to be clarified. Here we report the results of a comprehensive study of epitaxial junctions comprising BaTiO(3) barrier, La(0.7)Sr(0.3)MnO(3) bottom electrode and Au or Cu top electrodes. Our results demonstrate a giant electrode effect on the TER of these asymmetric FTJs. The revealed phenomena are attributed to the microscopic interfacial effect of ferroelectric origin, which is supported by the observation of redox-based resistance switching at much higher voltages.

  19. More about tunnelling times and superluminal tunnelling (Hartmann effect)

    International Nuclear Information System (INIS)

    Olkhovsky, V.S.; Recami, E.; Raciti, F.; Zaichenko, A.

    1995-05-01

    Aims of the present paper are: i) presenting and analysing the results of various numerical calculations on the penetration and return times Pen >, Ret >, during tunnelling inside a rectangular potential barrier, for various penetration depths x f ; ii) putting forth and discussing suitable definitions, besides of the mean values, also of the variances (or dispersions) D τT and D τR for the time durations of transmission and reflection processes; iii)mentioning, moreover, that our definition T > for the average transmission time results to constitute an improvement of the ordinary dwell- time formula; iv) commenting, at last, on the basis of the new numerical results, upon some recent criticism by C.R. Leavens. The paper stresses that numerical evaluations confirm that the approach implied, and implies, the existence of the Hartmann effect: an effect that in these days (due to the theoretical connections between tunnelling and evanescent-wave propagation) is receiving - at Cologne, Berkeley, Florence and Vienna - indirect, but quite interesting, experimental verification

  20. Interaction Driven Interband Tunneling of Bosons in the Triple Well

    OpenAIRE

    Cao, Lushuai; Brouzos, Ioannis; Zöllner, Sascha; Schmelcher, Peter

    2010-01-01

    We study the tunneling of a small ensemble of strongly repulsive bosons in a one-dimensional triple-well potential. The usual treatment within the single-band approximation suggests suppression of tunneling in the strong interaction regime. However, we show that several windows of enhanced tunneling are opened in this regime. This enhanced tunneling results from higher band contributions, and has the character of interband tunneling. It can give rise to various tunneling processes, such as si...

  1. CURRENT ASSET TUNNELING AND FIRM PERFORMANCE IN AN EMERGING MARKET

    OpenAIRE

    Ratna Candra Sari; Zaki Baridwan

    2014-01-01

    This study examines the effect of current asset tunneling on firm performance from the emerging market perspective. Although tunneling activities is a common practices by businesses especially in Indonesia, there exist obstacles in the measurement of tunneling activity because it is difficult to proof the existence of such practices. In this study, we measure tunneling by using accounts receivables and develop tunneling detection criteria. In addition, this study examines the effect of tunnel...

  2. Quantum tunnelling in condensed media

    CERN Document Server

    Kagan, Yu

    1992-01-01

    The essays in this book deal with of the problem of quantum tunnelling and related behavior of a microscopic or macroscopic system, which interacts strongly with an ""environment"" - this being some form of condensed matter. The ""system"" in question need not be physically distinct from its environment, but could, for example, be one particular degree of freedom on which attention is focussed, as in the case of the Josephson junction studied in several of the papers. This general problem has been studied in many hundreds, if not thousands, of articles in the literature, in contexts as diverse

  3. Quantum tunneling beyond semiclassical approximation

    International Nuclear Information System (INIS)

    Banerjee, Rabin; Majhi, Bibhas Ranjan

    2008-01-01

    Hawking radiation as tunneling by Hamilton-Jacobi method beyond semiclassical approximation is analysed. We compute all quantum corrections in the single particle action revealing that these are proportional to the usual semiclassical contribution. We show that a simple choice of the proportionality constants reproduces the one loop back reaction effect in the spacetime, found by conformal field theory methods, which modifies the Hawking temperature of the black hole. Using the law of black hole mechanics we give the corrections to the Bekenstein-Hawking area law following from the modified Hawking temperature. Some examples are explicitly worked out.

  4. Tunnelling from Goedel black holes

    International Nuclear Information System (INIS)

    Kerner, Ryan; Mann, R. B.

    2007-01-01

    We consider the spacetime structure of Kerr-Goedel black holes, analyzing their parameter space in detail. We apply the tunnelling method to compute their temperature and compare the results to previous calculations obtained via other methods. We claim that it is not possible to have the closed timelike curve (CTC) horizon in between the two black hole horizons and include a discussion of issues that occur when the radius of the CTC horizon is smaller than the radius of both black hole horizons

  5. Josephson tunnel junction microwave attenuator

    DEFF Research Database (Denmark)

    Koshelets, V. P.; Shitov, S. V.; Shchukin, A. V.

    1993-01-01

    A new element for superconducting electronic circuitry-a variable attenuator-has been proposed, designed, and successfully tested. The principle of operation is based on the change in the microwave impedance of a superconductor-insulator-superconductor (SIS) Josephson tunnel junction when dc biased...... at different points in the current-voltage characteristic. Both numerical calculations based on the Tien-Gordon theory and 70-GHz microwave experiments have confirmed the wide dynamic range (more than 15-dB attenuation for one stage) and the low insertion loss in the ''open'' state. The performance of a fully...

  6. Acute nephritic syndrome

    Science.gov (United States)

    Glomerulonephritis - acute; Acute glomerulonephritis; Nephritis syndrome - acute ... Acute nephritic syndrome is often caused by an immune response triggered by an infection or other disease. Common causes in children ...

  7. Computational Wind Tunnel: A Design Tool for Rotorcraft, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Rotorcraft engineers traditionally use the wind tunnel to evaluate and finalize designs. Insufficient correlation between wind tunnel results and flight tests, have...

  8. Tunneling of electrons through semiconductor superlattices

    Indian Academy of Sciences (India)

    Unknown

    Tunneling of electrons through semiconductor superlattices. C L ROY. Department of Physics and Meteorology, Indian Institute of Technology, Kharagpur 721 302, India. Abstract. The purpose of the present paper is to report a study of tunneling of electrons through semicon- ductor superlattices (SSL); specially, we have ...

  9. 49 CFR 177.810 - Vehicular tunnels.

    Science.gov (United States)

    2010-10-01

    ... through any urban vehicular tunnel used for mass transportation. [Amdt. 177-52, 46 FR 5316, Jan. 19, 1981... 49 Transportation 2 2010-10-01 2010-10-01 false Vehicular tunnels. 177.810 Section 177.810 Transportation Other Regulations Relating to Transportation PIPELINE AND HAZARDOUS MATERIALS SAFETY...

  10. Energy saving in tunnel entrance lighting.

    NARCIS (Netherlands)

    Schreuder, D.A. & Swart, L.

    1993-01-01

    Tunnel entrances may present themselves during the day as a "black hole" in which no details can be perceived. In order to ensure safe and comfortable driving at high speeds, the entrance zone must be lit to a high luminance level. Modern tunnel lighting technology is focused on two aspects:

  11. Object-Based Attention and Cognitive Tunneling

    Science.gov (United States)

    Jarmasz, Jerzy; Herdman, Chris M.; Johannsdottir, Kamilla Run

    2005-01-01

    Simulator-based research has shown that pilots cognitively tunnel their attention on head-up displays (HUDs). Cognitive tunneling has been linked to object-based visual attention on the assumption that HUD symbology is perceptually grouped into an object that is perceived and attended separately from the external scene. The present research…

  12. Transport of dangerous goods through road tunnels

    DEFF Research Database (Denmark)

    Jørgensen, N O; Lacroix, Didier; Amundsen, F.H.

    1999-01-01

    A paper which describes the work of an OECD research group. The group has suggested a grouping of dangerous materials, a quantitative risk assessment model and a decision support model which should allow tunnel operators to determine if a given material should be allowed throug a given tunnel...

  13. A Supermagnetic Tunnel Full of Subatomic Action

    CERN Document Server

    2008-01-01

    Last year, before the gigantic hadron supercollider at CERN research facility was installed underground, a photographer captured this picture of a 1,950 metric ton tunnel containing giant magnets that will be placed in a tunnel and kept at near-zero temperatures.

  14. Spin tunneling and manipulation in nanostructures.

    Science.gov (United States)

    Sherman, E Ya; Ban, Yue; Gulyaev, L V; Khomitsky, D V

    2012-09-01

    The results for joint effects of tunneling and spin-orbit coupling on spin dynamics in nanostructures are presented for systems with discrete and continuous spectra. We demonstrate that tunneling plays the crucial role in the spin dynamics and the abilities of spin manipulation by external electric field. This result can be important for design of nanostructures-based spintronics devices.

  15. Aeronautical Wind Tunnels, Europe and Asia

    Science.gov (United States)

    2006-02-01

    User Fees Contact Information Dr. Surjatin Wiriadidjaja, UPT-LAGG, BPP Teknologi, Puspiptek, Serpong, Tangerang 15310, Indonesia. Tel: (62) 21 756...of the tunnel, FFA T1500 Transonic Wind Tunnel Circuit (Sweden) manufactured by The Swedish Defense Research Agency (FOI). 2.4 m Transonic Wind

  16. Tunnel widening in anterior cruciate ligament reconstruction

    DEFF Research Database (Denmark)

    Clatworthy, M G; Annear, P; Bulow, J U

    1999-01-01

    We report a prospective series evaluating the incidence and degree of tunnel widening in a well-matched series of patients receiving a hamstring or patella tendon graft for anterior cruciate ligament (ACL) deficiency. We correlated tunnel widening with clinical factors, knee scores, KT-1000 and i...

  17. Flow-Based Detection of DNS Tunnels

    NARCIS (Netherlands)

    Ellens, W.; Żuraniewski, P.; Sperotto, A.; Schotanus, H.; Mandjes, M.; Meeuwissen, E.

    2013-01-01

    DNS tunnels allow circumventing access and security policies in firewalled networks. Such a security breach can be misused for activities like free web browsing, but also for command & control traffic or cyber espionage, thus motivating the search for effective automated DNS tunnel detection

  18. Flow-based detection of DNS tunnels

    NARCIS (Netherlands)

    Ellens, W.; Zuraniewski, P.; Schotanus, H.; Mandjes, M.R.H.; Meeuwissen, E.; Doyen, Guillaume; Waldburger, Martin; Celeda, Pavel; Sperotto, Anna; Stiller, Burkhard

    DNS tunnels allow circumventing access and security policies in firewalled networks. Such a security breach can be misused for activities like free web browsing, but also for command & control traffic or cyber espionage, thus motivating the search for effective automated DNS tunnel detection

  19. Flow-based detection of DNS tunnels

    NARCIS (Netherlands)

    Ellens, W.; Zuraniewski, P.W.; Sperotto, A.; Schotanus, H.A.; Mandjes, M.; Meeuwissen, H.B.

    2013-01-01

    DNS tunnels allow circumventing access and security policies in firewalled networks. Such a security breach can be misused for activities like free web browsing, but also for command & control traffic or cyber espionage, thus motivating the search for effective automated DNS tunnel detection

  20. On the directional selectivity of tunneling experiments

    International Nuclear Information System (INIS)

    Beuermann, G.; Goettingen Univ.

    1981-01-01

    Using realistic parameters in a simplified model the directional selectivity of tunneling experiments is discussed. Although perfect surfaces and barriers are assumed, quasiparticles coming from a wide solid angle may contribute essentially to the tunnel current. This must be taken into consideration in the case of gap anisotropy. (orig.)

  1. Road tunnels safety according to European legislation

    Directory of Open Access Journals (Sweden)

    Fedor KÁLLAY

    2008-01-01

    Full Text Available The article deals with safety of European road tunnels in accordance with actual European legislation. Standards and recommendations of European Commission, PIARC and other professional bodies of the European Union define minimal technological requirements for equipment and operation of the tunnels in scope of Trans-European Road Network.

  2. Time-resolved scanning tunnelling microscopy

    NARCIS (Netherlands)

    van Houselt, Arie; Zandvliet, Henricus J.W.

    2010-01-01

    Scanning tunneling microscopy has revolutionized our ability to image, study, and manipulate solid surfaces on the size scale of atoms. One important limitation of the scanning tunneling microscope (STM) is, however, its poor time resolution. Recording a standard image with a STM typically takes

  3. Temporary closure of the tunnel

    CERN Multimedia

    Relations with the Host States Service

    2005-01-01

    Owing to major maintenance work, the tunnel linking the various parts of the CERN site will be closed from Monday 4 July to Sunday 24 July 2005 The Host State authorities have given authorisation for persons employed by CERN or the Institutes to travel and for goods belonging to these entities to be transported between the various parts of the site via Gate E (Charles de Gaulle) while this work is being carried out, subject to strict compliance with the Rules for the Use of the Tunnel (see http://dsu.web.cern.ch/dsu/dsum/hsr/DOCUMENTS/8200980415.pdf). Gate E will thus be open between 7.00 a.m. and 7.00 p.m. from Monday to Friday during the period concerned. The rules governing the use of Gate E to enter the Meyrin site between 7.30 a.m. and 9.00 a.m. or to leave the site between 5.00 p.m. and 6.30 p.m. (see http://dsu.web.cern.ch/dsu/dsum/hsr/DOCUMENTS/12222_041027.pdf)) will remain unaffected by this temporary authorisation. Relations with the Host States Service and TS-FM Group

  4. Concept development for HLW disposal research tunnel

    International Nuclear Information System (INIS)

    Queon, S. K.; Kim, K. S.; Park, J. H.; Jeo, W. J.; Han, P. S.

    2003-01-01

    In order to dispose high-level radioactive waste in a geological formation, it is necessary to assess the safety of a disposal concept by excavating a research tunnel in the same geological formation as the host rock mass. The design concept of a research tunnel depends on the actual disposal concept, repository geometry, experiments to be carried at the tunnel, and geological conditions. In this study, analysis of the characteristics of the disposal research tunnel, which is planned to be constructed at KAERI site, calculation of the influence of basting impact on neighbor facilities, and computer simuation for mechanical stability analysis using a three-dimensional code, FLAC3D, had been carried out to develop the design concept of the research tunnel

  5. Quantum tunneling in the adiabatic Dicke model

    International Nuclear Information System (INIS)

    Chen Gang; Chen Zidong; Liang Jiuqing

    2007-01-01

    The Dicke model describes N two-level atoms interacting with a single-mode bosonic field and exhibits a second-order phase transition from the normal to the superradiant phase. The energy levels are not degenerate in the normal phase but have degeneracy in the superradiant phase, where quantum tunneling occurs. By means of the Born-Oppenheimer approximation and the instanton method in quantum field theory, the tunneling splitting, inversely proportional to the tunneling rate for the adiabatic Dicke model, in the superradiant phase can be evaluated explicitly. It is shown that the tunneling splitting vanishes as exp(-N) for large N, whereas for small N it disappears as √(N)/exp(N). The dependence of the tunneling splitting on the relevant parameters, especially on the atom-field coupling strength, is also discussed

  6. Tunneling Anomalous and Spin Hall Effects.

    Science.gov (United States)

    Matos-Abiague, A; Fabian, J

    2015-07-31

    We predict, theoretically, the existence of the anomalous Hall effect when a tunneling current flows through a tunnel junction in which only one of the electrodes is magnetic. The interfacial spin-orbit coupling present in the barrier region induces a spin-dependent momentum filtering in the directions perpendicular to the tunneling current, resulting in a skew tunneling even in the absence of impurities. This produces an anomalous Hall conductance and spin Hall currents in the nonmagnetic electrode when a bias voltage is applied across the tunneling heterojunction. If the barrier is composed of a noncentrosymmetric material, the anomalous Hall conductance and spin Hall currents become anisotropic with respect to both the magnetization and crystallographic directions, allowing us to separate this interfacial phenomenon from the bulk anomalous and spin Hall contributions. The proposed effect should be useful for proving and quantifying the interfacial spin-orbit fields in metallic and metal-semiconductor systems.

  7. High Surface Area Tunnels in Hexagonal WO₃.

    Science.gov (United States)

    Sun, Wanmei; Yeung, Michael T; Lech, Andrew T; Lin, Cheng-Wei; Lee, Chain; Li, Tianqi; Duan, Xiangfeng; Zhou, Jun; Kaner, Richard B

    2015-07-08

    High surface area in h-WO3 has been verified from the intracrystalline tunnels. This bottom-up approach differs from conventional templating-type methods. The 3.67 Å diameter tunnels are characterized by low-pressure CO2 adsorption isotherms with nonlocal density functional theory fitting, transmission electron microscopy, and thermal gravimetric analysis. These open and rigid tunnels absorb H(+) and Li(+), but not Na(+) in aqueous electrolytes without inducing a phase transformation, accessing both internal and external active sites. Moreover, these tunnel structures demonstrate high specific pseudocapacitance and good stability in an H2SO4 aqueous electrolyte. Thus, the high surface area created from 3.67 Å diameter tunnels in h-WO3 shows potential applications in electrochemical energy storage, selective ion transfer, and selective gas adsorption.

  8. Snow and ice blocking of tunnels

    Energy Technology Data Exchange (ETDEWEB)

    Lia, Leif

    1998-12-31

    Hydroelectric power development in cold regions causes much concern about operational reliability and dam safety. This thesis studies the temperature distribution in tunnels by means of air temperature measurements in six tunnel spillways and five diversion tunnels. The measurements lasted for two consecutive winters. The air through flow tunnel is used as it causes cooling of both rock and water. In open spillway tunnels, frost reaches the entire tunnel. In spillway tunnels with walls, the frost zones reach about 100 m from the downstream end. In mildly-inclined diversion tunnels, a frost free zone is located in the middle of the tunnel and snow and ice problems were only observed in the inlet and outlet. Severe aufeis is accumulation is observed in the frost zones. The heat transfer from rock to air, water and ice is calculated and used in a prediction model for the calculation of aufeis build-up together with local field observation data. The water penetration of snow plugs is also calculated, based on the heat balance. It takes 20 to 50 days for water to enter the blocked tunnel. The empirical values are 30 to 60 days, but only 1 day if the temperature of the snow pack is 0{sup o}C. Sensitivity analyses are carried out for temperature variations in rock, snow, water and ice. Systematic field observation shows that it is important for hydropower companies to know about the effects of snow and ice blocking in an area. A risk analysis of dam safety is presented for a real case. Finally, the thesis proposes solutions which can reduce the snow and ice problems. 79 refs., 63 figs., 11 tabs.

  9. Influence of trap-assisted tunneling on trap-assisted tunneling current in double gate tunnel field-effect transistor

    Science.gov (United States)

    Zhi, Jiang; Yi-Qi, Zhuang; Cong, Li; Ping, Wang; Yu-Qi, Liu

    2016-02-01

    Trap-assisted tunneling (TAT) has attracted more and more attention, because it seriously affects the sub-threshold characteristic of tunnel field-effect transistor (TFET). In this paper, we assess subthreshold performance of double gate TFET (DG-TFET) through a band-to-band tunneling (BTBT) model, including phonon-assisted scattering and acoustic surface phonons scattering. Interface state density profile (Dit) and the trap level are included in the simulation to analyze their effects on TAT current and the mechanism of gate leakage current. Project supported by the National Natural Science Foundation of China (Grant Nos. 61574109 and 61204092).

  10. Influence of trap-assisted tunneling on trap-assisted tunneling current in double gate tunnel field-effect transistor

    International Nuclear Information System (INIS)

    Jiang Zhi; Zhuang Yi-Qi; Li Cong; Wang Ping; Liu Yu-Qi

    2016-01-01

    Trap-assisted tunneling (TAT) has attracted more and more attention, because it seriously affects the sub-threshold characteristic of tunnel field-effect transistor (TFET). In this paper, we assess subthreshold performance of double gate TFET (DG-TFET) through a band-to-band tunneling (BTBT) model, including phonon-assisted scattering and acoustic surface phonons scattering. Interface state density profile (D it ) and the trap level are included in the simulation to analyze their effects on TAT current and the mechanism of gate leakage current. (paper)

  11. Homoepitaxial graphene tunnel barriers for spin transport

    Directory of Open Access Journals (Sweden)

    Adam L. Friedman

    2016-05-01

    Full Text Available Tunnel barriers are key elements for both charge-and spin-based electronics, offering devices with reduced power consumption and new paradigms for information processing. Such devices require mating dissimilar materials, raising issues of heteroepitaxy, interface stability, and electronic states that severely complicate fabrication and compromise performance. Graphene is the perfect tunnel barrier. It is an insulator out-of-plane, possesses a defect-free, linear habit, and is impervious to interdiffusion. Nonetheless, true tunneling between two stacked graphene layers is not possible in environmental conditions usable for electronics applications. However, two stacked graphene layers can be decoupled using chemical functionalization. Here, we demonstrate that hydrogenation or fluorination of graphene can be used to create a tunnel barrier. We demonstrate successful tunneling by measuring non-linear IV curves and a weakly temperature dependent zero-bias resistance. We demonstrate lateral transport of spin currents in non-local spin-valve structures, and determine spin lifetimes with the non-local Hanle effect. We compare the results for hydrogenated and fluorinated tunnel and we discuss the possibility that ferromagnetic moments in the hydrogenated graphene tunnel barrier affect the spin transport of our devices.

  12. Homoepitaxial graphene tunnel barriers for spin transport

    Science.gov (United States)

    Friedman, Adam L.; van't Erve, Olaf M. J.; Robinson, Jeremy T.; Whitener, Keith E.; Jonker, Berend T.

    2016-05-01

    Tunnel barriers are key elements for both charge-and spin-based electronics, offering devices with reduced power consumption and new paradigms for information processing. Such devices require mating dissimilar materials, raising issues of heteroepitaxy, interface stability, and electronic states that severely complicate fabrication and compromise performance. Graphene is the perfect tunnel barrier. It is an insulator out-of-plane, possesses a defect-free, linear habit, and is impervious to interdiffusion. Nonetheless, true tunneling between two stacked graphene layers is not possible in environmental conditions usable for electronics applications. However, two stacked graphene layers can be decoupled using chemical functionalization. Here, we demonstrate that hydrogenation or fluorination of graphene can be used to create a tunnel barrier. We demonstrate successful tunneling by measuring non-linear IV curves and a weakly temperature dependent zero-bias resistance. We demonstrate lateral transport of spin currents in non-local spin-valve structures, and determine spin lifetimes with the non-local Hanle effect. We compare the results for hydrogenated and fluorinated tunnel and we discuss the possibility that ferromagnetic moments in the hydrogenated graphene tunnel barrier affect the spin transport of our devices.

  13. Signatures of unstable semiclassical trajectories in tunneling

    International Nuclear Information System (INIS)

    Levkov, D G; Panin, A G; Sibiryakov, S M

    2009-01-01

    It was found recently that processes of multidimensional tunneling are generally described at high energies by unstable semiclassical trajectories. We study two observational signatures related to the instability of trajectories. First, we find an additional power-law dependence of the tunneling probability on the semiclassical parameter as compared to the standard case of potential tunneling. The second signature is a substantial widening of the probability distribution over final-state quantum numbers. These effects are studied using a modified semiclassical technique which incorporates stabilization of the tunneling trajectories. The technique is derived from first principles. We obtain expressions for the inclusive and exclusive tunneling probabilities in the case of unstable semiclassical trajectories. We also investigate the 'phase transition' between the cases of stable and unstable trajectories across certain 'critical' values of energy. Finally, we derive the relation between the semiclassical probabilities of tunneling from the low-lying and highly excited initial states. This puts on firm ground a conjecture made previously in the semiclassical description of collision-induced tunneling in field theory

  14. Investigation into scanning tunnelling luminescence microscopy

    International Nuclear Information System (INIS)

    Manson-Smith, S.K.

    2001-01-01

    This work reports on the development of a scanning tunnelling luminescence (STL) microscope and its application to the study of Ill-nitride semiconductor materials used in the production of light emitting devices. STL microscopy is a technique which uses the high resolution topographic imaging capabilities of the scanning tunnelling microscope (STM) to generate high resolution luminescence images. The STM tunnelling current acts as a highly localised source of electrons (or holes) which generates luminescence in certain materials. Light generated at the STM tunnelling junction is collected concurrently with the height variation of the tunnelling probe as it is scanned across a sample surface, producing simultaneous topographic and luminescence images. Due to the very localised excitation source, high resolution luminescence images can be obtained. Spectroscopic resolution can be obtained by using filters. Additionally, the variation of luminescence intensity with tunnel current and with bias voltage can provide information on recombination processes and material properties. The design and construction of a scanning tunnelling luminescence microscope is described in detail. Operating under ambient conditions, the microscope has several novel features, including a new type of miniature inertial slider-based approach motor, large solid-angle light collection optical arrangement and a tip-height regulation system which requires the minimum of operator input. (author)

  15. Tunnel effect wave energy detection

    Science.gov (United States)

    Kaiser, William J. (Inventor); Waltman, Steven B. (Inventor); Kenny, Thomas W. (Inventor)

    1995-01-01

    Methods and apparatus for measuring gravitational and inertial forces, magnetic fields, or wave or radiant energy acting on an object or fluid in space provide an electric tunneling current through a gap between an electrode and that object or fluid in space and vary that gap with any selected one of such forces, magnetic fields, or wave or radiant energy acting on that object or fluid. These methods and apparatus sense a corresponding variation in an electric property of that gap and determine the latter force, magnetic fields, or wave or radiant energy in response to that corresponding variation, and thereby sense or measure such parameters as acceleration, position, particle mass, velocity, magnetic field strength, presence or direction, or wave or radiant energy intensity, presence or direction.

  16. Acute Pancreatitis and Pregnancy

    Science.gov (United States)

    ... Pancreatitis Acute Pancreatitis and Pregnancy Acute Pancreatitis and Pregnancy Timothy Gardner, MD Acute pancreatitis is defined as ... pancreatitis in pregnancy. Reasons for Acute Pancreatitis and Pregnancy While acute pancreatitis is responsible for almost 1 ...

  17. The Thames Tideway Tunnel (3/3)

    CERN Multimedia

    CERN. Geneva

    2012-01-01

    Lecture 3: Insight into a pioneering project at the cutting edge of engineering: the upgrade to London’s failing sewerage system. With a growing population and heavier rainfall, the River Thames is regularly polluted in breach of European Directive requirements. Two new storage and transfer tunnels will run up to 85m deep under the river and will intercept and divert sewer overflows to a treatment facility in east London. The challenges faced by constructing a tunnel project of this size under the river and through London’s historic urban environment will set a new UK record for this type of tunnelling.

  18. Towards vortex imaging with scanning tunneling microscope

    International Nuclear Information System (INIS)

    Fuchs, Dan T.

    1994-02-01

    A low temperature, Besocke beetle type scanning tunneling microscope, with a scan range of 10 by 10 microns was built. The scanning tunneling microscope was calibrates for various temperatures and tested on several samples. Gold monolayers evaporated at 400 deg C were resolved and their dynamic behavior observed. Atomic resolution images of graphite were obtained. The scanning tunneling microscope was designed for future applications of vortex imaging in superconductors. The special design considerations for this application are discussed and the physics underlying it reviewed. (author)

  19. Scanning Tunneling Microscope For Use In Vacuum

    Science.gov (United States)

    Abel, Phillip B.

    1993-01-01

    Scanning tunneling microscope with subangstrom resolution developed to study surface structures. Although instrument used in air, designed especially for use in vacuum. Scanning head is assembly of small, mostly rigid components made of low-outgassing materials. Includes coarse-positioning mechanical-translation stage, on which specimen mounted by use of standard mounting stub. Tunneling tip mounted on piezoelectric fine-positioning tube. Application of suitable voltages to electrodes on piezoelectric tube controls scan of tunneling tip across surface of specimen. Electronic subsystem generates scanning voltages and collects data.

  20. Hard rock tunneling using pulsed electron beams

    International Nuclear Information System (INIS)

    Avery, R.T.; Brekke, T.L.; Finnie, I.

    1974-01-01

    Intense submicrosecond bursts of energetic electrons cause significant pulverization and surface spalling of a variety of rock types, the spall debris generally consisting of sand, dust, and small flakes. If carried out at rapid repetition rate this can lead to a promising technique for increasing the speed and reducing the cost of underground excavation of tunnels, mines, and storage spaces. The conceptual design features of a Pulsed Electron Tunnel Excavator capable of tunneling approximately ten times faster than conventional drill/blast methods were studied. (auth)

  1. Mechanical tunnel excavation in welded tuff

    International Nuclear Information System (INIS)

    Sperry, P.E.

    1991-01-01

    The Technical Review Board for the US high-level radioactive waste facility at Yucca Mountain has recommended maximum use of open-quotes the most modern mechanical excavation techniques...in order to reduce disturbance to the rock walls and to achieve greater economy of time and cost.close quotes Tunnels for the waste repository at Yucca Mountain can be economically constructed with mechanical excavation equipment. This paper presents the results of mechanical excavation of a tunnel in welded tuff, similar to the tuffs of Yucca Mountain. These results are projected to excavation of emplacement drifts in Yucca Mountain using a current state-of-the-art tunnel boring machine (TBM)

  2. Integrated tunneling sensor for nanoelectromechanical systems

    DEFF Research Database (Denmark)

    Sadewasser, S.; Abadal, G.; Barniol, N.

    2006-01-01

    Transducers based on quantum mechanical tunneling provide an extremely sensitive sensor principle, especially for nanoelectromechanical systems. For proper operation a gap between the electrodes of below 1 nm is essential, requiring the use of structures with a mobile electrode. At such small...... distances, attractive van der Waals and capillary forces become sizable, possibly resulting in snap-in of the electrodes. The authors present a comprehensive analysis and evaluation of the interplay between the involved forces and identify requirements for the design of tunneling sensors. Based...... on this analysis, a tunneling sensor is fabricated by Si micromachining technology and its proper operation is demonstrated. (c) 2006 American Institute of Physics....

  3. Tunneling decay of self-gravitating vortices

    Directory of Open Access Journals (Sweden)

    Dupuis Éric

    2018-01-01

    Full Text Available We investigate tunneling decay of false vortices in the presence of gravity, in which vortices are trapped in the false vacuum of a theory of scalar electrodynamics in three dimensions. The core of the vortex contains magnetic flux in the true vacuum, while outside the vortex is the appropriate topologically nontrivial false vacuum. We numerically obtain vortex solutions which are classically stable; however, they could decay via tunneling. To show this phenomenon, we construct the proper junction conditions in curved spacetime. We find that the tunneling exponent for the vortices is half that for Coleman-de Luccia bubbles and discuss possible future applications.

  4. Tunneling spin injection into single layer graphene.

    Science.gov (United States)

    Han, Wei; Pi, K; McCreary, K M; Li, Yan; Wong, Jared J I; Swartz, A G; Kawakami, R K

    2010-10-15

    We achieve tunneling spin injection from Co into single layer graphene (SLG) using TiO₂ seeded MgO barriers. A nonlocal magnetoresistance (ΔR(NL)) of 130  Ω is observed at room temperature, which is the largest value observed in any material. Investigating ΔR(NL) vs SLG conductivity from the transparent to the tunneling contact regimes demonstrates the contrasting behaviors predicted by the drift-diffusion theory of spin transport. Furthermore, tunnel barriers reduce the contact-induced spin relaxation and are therefore important for future investigations of spin relaxation in graphene.

  5. Intrinsic Tunneling in Phase Separated Manganites

    Science.gov (United States)

    Singh-Bhalla, G.; Selcuk, S.; Dhakal, T.; Biswas, A.; Hebard, A. F.

    2009-02-01

    We present evidence of direct electron tunneling across intrinsic insulating regions in submicrometer wide bridges of the phase-separated ferromagnet (La,Pr,Ca)MnO3. Upon cooling below the Curie temperature, a predominantly ferromagnetic supercooled state persists where tunneling across the intrinsic tunnel barriers (ITBs) results in metastable, temperature-independent, high-resistance plateaus over a large range of temperatures. Upon application of a magnetic field, our data reveal that the ITBs are extinguished resulting in sharp, colossal, low-field resistance drops. Our results compare well to theoretical predictions of magnetic domain walls coinciding with the intrinsic insulating phase.

  6. Application of fuzzy methods in tunnelling

    Directory of Open Access Journals (Sweden)

    Ľudmila Tréfová

    2011-12-01

    Full Text Available Full-face tunnelling machines were used for the tunnel construction in Slovakia for boring of the exploratory galleries of highwaytunnels Branisko and Višňové-Dubná skala. A monitoring system of boring process parameters was installed on the tunnelling machinesand the acquired outcomes were processed by several theoretical approaches. Method IKONA was developed for the determination ofchanges in the rock mass strength characteristics in the line of exploratory gallery. Individual geological sections were evaluated bythe descriptive statistics and the TBM performance was evaluated by the fuzzy method. The paper informs on the procedure of the designof fuzzy models and their verification.

  7. Thermal stability of tunneling spin polarization

    International Nuclear Information System (INIS)

    Kant, C.H.; Kohlhepp, J.T.; Paluskar, P.V.; Swagten, H.J.M.; Jonge, W.J.M. de

    2005-01-01

    We present a study of the thermal stability of tunneling spin polarization in Al/AlOx/ferromagnet junctions based on the spin-polarized tunneling technique, in which the Zeeman-split superconducting density of states in the Al electrode is used as a detector for the spin polarization. Thermal robustness of the polarization, which is of key importance for the performance of magnetic tunnel junction devices, is demonstrated for post-deposition anneal temperatures up to 500 o C with Co and Co 90 Fe 10 top electrodes, independent of the presence of an FeMn layer on top of the ferromagnet

  8. Tunneling rates in electron transport through double-barrier molecular junctions in a scanning tunneling microscope.

    Science.gov (United States)

    Nazin, G V; Wu, S W; Ho, W

    2005-06-21

    The scanning tunneling microscope enables atomic-scale measurements of electron transport through individual molecules. Copper phthalocyanine and magnesium porphine molecules adsorbed on a thin oxide film grown on the NiAl(110) surface were probed. The single-molecule junctions contained two tunneling barriers, vacuum gap, and oxide film. Differential conductance spectroscopy shows that electron transport occurs via vibronic states of the molecules. The intensity of spectral peaks corresponding to the individual vibronic states depends on the relative electron tunneling rates through the two barriers of the junction, as found by varying the vacuum gap tunneling rate by changing the height of the scanning tunneling microscope tip above the molecule. A simple, sequential tunneling model explains the observed trends.

  9. Influence of quasiparticle multi-tunneling on the energy flow through the superconducting tunnel junction

    International Nuclear Information System (INIS)

    Samedov, V. V.; Tulinov, B. M.

    2011-01-01

    Superconducting tunnel junction (STJ) detector consists of two layers of superconducting material separated by thin insulating barrier. An incident particle produces in superconductor excess nonequilibrium quasiparticles. Each quasiparticle in superconductor should be considered as quantum superposition of electron-like and hole-like excitations. This duality nature of quasiparticle leads to the effect of multi-tunneling. Quasiparticle starts to tunnel back and forth through the insulating barrier. After tunneling from biased electrode quasiparticle loses its energy via phonon emission. Eventually, the energy that equals to the difference in quasiparticle energy between two electrodes is deposited in the signal electrode. Because of the process of multi-tunneling, one quasiparticle can deposit energy more than once. In this work, the theory of branching cascade processes was applied to the process of energy deposition caused by the quasiparticle multi-tunneling. The formulae for the mean value and variance of the energy transferred by one quasiparticle into heat were derived. (authors)

  10. Apparatus and method for large tunnel excavation in hard rock

    International Nuclear Information System (INIS)

    Altseimer, J.H.; Hanold, R.J.

    1975-01-01

    A tunneling machine is described for producing large tunnels in rock by progressive detachment of the tunnel core by thermal melting a boundary kerf into the tunnel face and simultaneously forming an initial tunnel wall support by deflecting the molten materials against the tunnel walls to provide, when solidified, a continuous liner; and fragmenting the tunnel core circumscribed by the kerf by thermal stress fracturing and in which the heat required for such operations is supplied by a compact nuclear reactor. (U.S.)

  11. Trap assisted tunneling and its effect on subthreshold swing of tunnel field effect transistors

    OpenAIRE

    Sajjad, Redwan N.; Chern, Winston; Hoyt, Judy L.; Antoniadis, Dimitri A.

    2016-01-01

    We provide a detailed study of the interface Trap Assisted Tunneling (TAT) mechanism in tunnel field effect transistors to show how it contributes a major leakage current path before the Band To Band Tunneling (BTBT) is initiated. With a modified Shockley-Read-Hall formalism, we show that at room temperature, the phonon assisted TAT current always dominates and obscures the steep turn ON of the BTBT current for common densities of traps. Our results are applicable to top gate, double gate and...

  12. Tunneling time, exit time and exit momentum in strong field tunnel ionization

    International Nuclear Information System (INIS)

    Teeny, Nicolas

    2016-01-01

    Tunnel ionization belongs to the fundamental processes of atomic physics. It is still an open question when does the electron tunnel ionize and how long is the duration of tunneling. In this work we solve the time-dependent Schroedinger equation in one and two dimensions and use ab initio quantum calculations in order to answer these questions. Additionally, we determine the exit momentum of the tunnel ionized electron from first principles. We find out results that are different from the assumptions of the commonly employed two-step model, which assumes that the electron ionizes at the instant of electric field maximum with a zero momentum. After determining the quantum final momentum distribution of tunnel ionized electrons we show that the two-step model fails to predict the correct final momentum. Accordingly we suggest how to correct the two-step model. Furthermore, we determine the instant at which tunnel ionization starts, which turns out to be different from the instant usually assumed. From determining the instant at which it is most probable for the electron to enter the tunneling barrier and the instant at which it exits we determine the most probable time spent under the barrier. Moreover, we apply a quantum clock approach in order to determine the duration of tunnel ionization. From the quantum clock we determine an average tunneling time which is different in magnitude and origin with respect to the most probable tunneling time. By defining a probability distribution of tunneling times using virtual detectors we relate both methods and explain the apparent discrepancy. The results found have in general an effect on the interpretation of experiments that measure the spectra of tunnel ionized electrons, and specifically on the calibration of the so called attoclock experiments, because models with imprecise assumptions are usually employed in order to interpret experimental results.

  13. Tunneling time, exit time and exit momentum in strong field tunnel ionization

    Energy Technology Data Exchange (ETDEWEB)

    Teeny, Nicolas

    2016-10-18

    Tunnel ionization belongs to the fundamental processes of atomic physics. It is still an open question when does the electron tunnel ionize and how long is the duration of tunneling. In this work we solve the time-dependent Schroedinger equation in one and two dimensions and use ab initio quantum calculations in order to answer these questions. Additionally, we determine the exit momentum of the tunnel ionized electron from first principles. We find out results that are different from the assumptions of the commonly employed two-step model, which assumes that the electron ionizes at the instant of electric field maximum with a zero momentum. After determining the quantum final momentum distribution of tunnel ionized electrons we show that the two-step model fails to predict the correct final momentum. Accordingly we suggest how to correct the two-step model. Furthermore, we determine the instant at which tunnel ionization starts, which turns out to be different from the instant usually assumed. From determining the instant at which it is most probable for the electron to enter the tunneling barrier and the instant at which it exits we determine the most probable time spent under the barrier. Moreover, we apply a quantum clock approach in order to determine the duration of tunnel ionization. From the quantum clock we determine an average tunneling time which is different in magnitude and origin with respect to the most probable tunneling time. By defining a probability distribution of tunneling times using virtual detectors we relate both methods and explain the apparent discrepancy. The results found have in general an effect on the interpretation of experiments that measure the spectra of tunnel ionized electrons, and specifically on the calibration of the so called attoclock experiments, because models with imprecise assumptions are usually employed in order to interpret experimental results.

  14. PREFERED SURGICAL TECHNIQUE USED BY ORTHOPEDISTS IN ACUTE ACROMIOCLAVICULAR DISLOCATION

    Science.gov (United States)

    NISHIMI, ALEXANDRE YUKIO; ARBEX, DEMETRIO SIMÃO; MARTINS, DIOGO LUCAS CAMPOS; GUSMÃO, CARLOS VINICIUS BUARQUE DE; BONGIOVANNI, ROBERTO RANGEL; PASCARELLI, LUCIANO

    2016-01-01

    ABSTRACT Objective: To determine whether training on shoulder and elbow surgery influences the orthopedist surgeons' preferred technique to address acute acromioclavicular joint dislocation (ACD). Methods: A survey was conducted with shoulder and elbow specialists and general orthopedists on their preferred technique to address acute ACD. Results: Thirty specialists and forty-five general orthopedists joined the study. Most specialists preferred the endobutton technique, while most general orthopedists preferred the modified Phemister procedure for coracoclavicular ligament repair using anchors. We found no difference between specialists and general orthopedists in the number of tunnels used to repair the coracoclavicular ligament; preferred method for wire insertion through the clavicular tunnels; buried versus unburied Kirschner wire insertion for acromioclavicular temporary fixation; and time for its removal; and regarding the suture thread used for deltotrapezoidal fascia closure. Conclusion: Training on shoulder and elbow surgery influences the surgeons' preferred technique to address acute ACD. Level of Evidence V, Expert Opinion. PMID:28149190

  15. Acute pancreatitis.

    Science.gov (United States)

    Talukdar, Rupjyoti; Vege, Santhi S

    2015-09-01

    To summarize recent data on classification systems, cause, risk factors, severity prediction, nutrition, and drug treatment of acute pancreatitis. Comparison of the Revised Atlanta Classification and Determinant Based Classification has shown heterogeneous results. Simvastatin has a protective effect against acute pancreatitis. Young black male, alcohol, smoldering symptoms, and subsequent diagnosis of chronic pancreatitis are risk factors associated with readmissions after acute pancreatitis. A reliable clinical or laboratory marker or a scoring system to predict severity is lacking. The PYTHON trial has shown that oral feeding with on demand nasoenteric tube feeding after 72 h is as good as nasoenteric tube feeding within 24 h in preventing infections in predicted severe acute pancreatitis. Male sex, multiple organ failure, extent of pancreatic necrosis, and heterogeneous collection are factors associated with failure of percutaneous drainage of pancreatic collections. The newly proposed classification systems of acute pancreatitis need to be evaluated more critically. New biomarkers are needed for severity prediction. Further well designed studies are required to assess the type of enteral nutritional formulations for acute pancreatitis. The optimal minimally invasive method or combination to debride the necrotic collections is evolving. There is a great need for a drug to treat the disease early on to prevent morbidity and mortality.

  16. Quantum size effects on spin-tunneling time in a magnetic resonant tunneling diode

    OpenAIRE

    Saffarzadeh, Alireza; Daqiq, Reza

    2009-01-01

    We study theoretically the quantum size effects of a magnetic resonant tunneling diode (RTD) with a (Zn,Mn)Se dilute magnetic semiconductor layer on the spin-tunneling time and the spin polarization of the electrons. The results show that the spin-tunneling times may oscillate and a great difference between the tunneling time of the electrons with opposite spin directions can be obtained depending on the system parameters. We also study the effect of structural asymmetry which is related to t...

  17. Seismic prediction ahead of tunnel construction using Rayleigh-waves

    OpenAIRE

    Jetschny, Stefan; De Nil, Denise; Bohlen, Thomas

    2008-01-01

    To increase safety and efficiency of tunnel constructions, online seismic exploration ahead of a tunnel can become a valuable tool. We developed a new forward looking seismic imaging technique e.g. to determine weak and water bearing zones ahead of the constructions. Our approach is based on the excitation and registration of tunnel surface-waves. These waves are excited at the tunnel face behind the cutter head of a tunnel boring machine and travel into drilling direction. Arriving at the fr...

  18. 7 x 10 Foot Wind Tunnel

    Data.gov (United States)

    Federal Laboratory Consortium — This wind tunnel is used for basic and applied research in aeromechanics on advanced and unique technology rotorcraft. It supports research on advanced concepts and...

  19. Engineering a de Novo Transport Tunnel

    Czech Academy of Sciences Publication Activity Database

    Březovský, J.; Babková, P.; Degtjarik, Oksana; Fořtová, A.; Gora, A.; Iermak, Iuliia; Řezáčová, Pavlína; Dvořák, P.; Kutá Smatanová, Ivana; Prokop, Z.; Chaloupková, R.; Damborský, J.

    2016-01-01

    Roč. 6, č. 11 (2016), s. 7597-7610 ISSN 2155-5435 Institutional support: RVO:61388971 ; RVO:68378050 Keywords : transport tunnel * protein engineering * protein design Subject RIV: EE - Microbiology, Virology Impact factor: 10.614, year: 2016

  20. Computer graphic of LHC in the tunnel

    CERN Multimedia

    1996-01-01

    A computer-generated image of the LHC particle accelerator at CERN in the tunnel originally built for the LEP accelerator that was closed in 2000. The cross-section of an LHC superconducting dipole magnet is also seen.

  1. LEP sees the end of the tunnel

    CERN Multimedia

    2002-01-01

    After 14 months, which have seen the removal of 30,000 tonnes of material from the tunnel, the LEP dismantling operation has now been completed. LHC installation, which will be subject to new safety rules, can go ahead.

  2. A century of wind tunnels since Eiffel

    Science.gov (United States)

    Chanetz, Bruno

    2017-08-01

    Fly higher, faster, preserve the life of test pilots and passengers, many challenges faced by man since the dawn of the twentieth century, with aviation pioneers. Contemporary of the first aerial exploits, wind tunnels, artificially recreating conditions encountered during the flight, have powerfully contributed to the progress of aeronautics. But the use of wind tunnels is not limited to aviation. The research for better performance, coupled with concern for energy saving, encourages manufacturers of ground vehicles to perform aerodynamic tests. Buildings and bridge structures are also concerned. This article deals principally with the wind tunnels built at ONERA during the last century. Somme wind tunnels outside ONERA, even outside France, are also evocated when their characteristics do not exist at ONERA.

  3. Low Speed Wind Tunnel Facility (LSWTF)

    Data.gov (United States)

    Federal Laboratory Consortium — Description: This facility consists of a large-scale, low-speed open-loop induction wind tunnel which has been modified to house a linear turbine cascade. A 125-hp...

  4. Dielectric Sensors Based on Electromagnetic Energy Tunneling

    Science.gov (United States)

    Siddiqui, Omar; Kashanianfard, Mani; Ramahi, Omar

    2015-01-01

    We show that metallic wires embedded in narrow waveguide bends and channels demonstrate resonance behavior at specific frequencies. The electromagnetic energy at these resonances tunnels through the narrow waveguide channels with almost no propagation losses. Under the tunneling behavior, high-intensity electromagnetic fields are produced in the vicinity of the metallic wires. These intense field resonances can be exploited to build highly sensitive dielectric sensors. The sensor operation is explained with the help of full-wave simulations. A practical setup consisting of a 3D waveguide bend is presented to experimentally observe the tunneling phenomenon. The tunneling frequency is predicted by determining the input impedance minima through a variational formula based on the Green function of a probe-excited parallel plate waveguide. PMID:25835188

  5. Tunneling time in space fractional quantum mechanics

    Science.gov (United States)

    Hasan, Mohammad; Mandal, Bhabani Prasad

    2018-02-01

    We calculate the time taken by a wave packet to travel through a classically forbidden region of space in space fractional quantum mechanics. We obtain the close form expression of tunneling time from a rectangular barrier by stationary phase method. We show that tunneling time depends upon the width b of the barrier for b → ∞ and therefore Hartman effect doesn't exist in space fractional quantum mechanics. Interestingly we found that the tunneling time monotonically reduces with increasing b. The tunneling time is smaller in space fractional quantum mechanics as compared to the case of standard quantum mechanics. We recover the Hartman effect of standard quantum mechanics as a special case of space fractional quantum mechanics.

  6. Air quality assessment in Salim Slam Tunnel

    International Nuclear Information System (INIS)

    El-Fadel, M.; Hashisho, Z.; Saikaly, P.

    1999-01-01

    Full text.Vehicle emissions constitute a serious occupational environmental hazard particularly in confined spaces such as tunnels and underground parking garages. these emissions at elevated concentrations, can cause adverse health effects, which range from nausea and eye irritation to mutagenicity, carcinogenicity and even death. This paper presents an environmental air quality assessment in a tunnel located in a highly congested urban area. For this purpose, air samples were collected and analyzed for the presence of primary air pollutants, priority metals, and volatile organic carbons. Air quality modeling was conducted to simulate variations of pollutant concentrations in the tunnel under worst case scenarios including traffic congestion and no air ventilation. Field measurements and mathematical simulation results were used to develop a strategy for proper air quality management in tunnels

  7. Tunnel magnetoresistance in double spin filter junctions

    International Nuclear Information System (INIS)

    Saffarzadeh, Alireza

    2003-01-01

    We consider a new type of magnetic tunnel junction, which consists of two ferromagnetic tunnel barriers acting as spin filters (SFs), separated by a nonmagnetic metal (NM) layer. Using the transfer matrix method and the free-electron approximation, the dependence of the tunnel magnetoresistance (TMR) on the thickness of the central NM layer, bias voltage and temperature in the double SF junction are studied theoretically. It is shown that the TMR and electron-spin polarization in this structure can reach very large values under suitable conditions. The highest value of the TMR can reach 99%. By an appropriate choice of the thickness of the central NM layer, the degree of spin polarization in this structure will be higher than that of the single SF junctions. These results may be useful in designing future spin-polarized tunnelling devices

  8. Proton tunnelling in intermolecular hydrogen bonds

    Energy Technology Data Exchange (ETDEWEB)

    Horsewill, A J [Nottingham Univ. (United Kingdom); Johnson, M R [Institut Max von Laue - Paul Langevin (ILL), 38 - Grenoble (France); Trommsdorff, H P [Grenoble-1 Univ., 38 (France)

    1997-04-01

    The wavefunctions of particles extend beyond the classically accessible regions of potential energy-surfaces (PES). A manifestation of this partial delocalization is the quantum-mechanical tunneling effect which enables a particle to escape from a metastable potential-well. Tunnelling is most important for the lightest atoms, so that the determination of its contribution to proton transfer, one of the most fundamental chemical reactions, is an important issue. QENS and NMR techniques have been employed to study the motion of protons in the hydrogen bond of benzoic-acid crystals, a system which has emerged as a particularly suitable model since proton transfer occurs in a near symmetric double-well potential. The influence of quantum tunnelling was revealed and investigated in these experiments. This work provides an experimental benchmark for theoretical descriptions of translational proton-tunnelling. (author). 7 refs.

  9. TBM tunneling on the Yucca Mountain Project

    International Nuclear Information System (INIS)

    Morris, J.P.; Hansmire, W.H.

    1995-01-01

    The US Department of Energy's (DOE) Yucca Mountain Project (YMP) is a scientific endeavor to determine the suitability of Yucca Mountain for the first long-term, high-level nuclear waste repository in the United States. The current status of this long-term project from the construction perspective is described. A key element is construction of the Exploratory Studies Facility (ESF) Tunnel, which is being excavated with a 7.6 m (25 ft) diameter tunnel boring machine (TBM). Development of the ESF may include the excavation of over 15 km (9.3 mi) of tunnel varying in size from 3.0 to 7.6 m (10 to 25 ft). Prior to construction, extensive constructability reviews were an interactive part of the final design. The intent was to establish a constructable design that met the long-term stability requirements for radiological safety of a future repository, while maintaining flexibility for the scientific investigations and acceptable tunneling productivity

  10. Dynamical quenching of tunneling in molecular magnets

    Energy Technology Data Exchange (ETDEWEB)

    José Santander, María, E-mail: maria.jose.noemi@gmail.com [Recursos Educativos Quántica, Santiago (Chile); Departamento de Física, Universidad de Santiago de Chile and CEDENNA, Avda. Ecuador 3493, Santiago (Chile); Nunez, Alvaro S., E-mail: alnunez@dfi.uchile.cl [Departamento de Física, Facultad de Ciencias Físicas y Matemáticas, Universidad de Chile, Casilla 487-3, Santiago (Chile); Roldán-Molina, A. [Instituto de Física, Pontificia Universidad Católica de Valparaíso, Avenida Universidad 330, Curauma, Valparaíso (Chile); Troncoso, Roberto E., E-mail: r.troncoso.c@gmail.com [Centro para el Desarrollo de la Nanociencia y la Nanotecnología, CEDENNA, Avda. Ecuador 3493, Santiago 9170124 (Chile); Departamento de Física, Universidad Técnica Federico Santa María, Avenida España 1680, Valparaíso (Chile)

    2015-12-15

    It is shown that a single molecular magnet placed in a rapidly oscillating magnetic field displays the phenomenon of quenching of tunneling processes. The results open a way to manipulate the quantum states of molecular magnets by means of radiation in the terahertz range. Our analysis separates the time evolution into slow and fast components thereby obtaining an effective theory for the slow dynamics. This effective theory presents quenching of the tunnel effect, in particular, stands out its difference with the so-called coherent destruction of tunneling. We support our prediction with numerical evidence based on an exact solution of Schrödinger's equation. - Highlights: • Single molecular magnets under rapidly oscillating magnetic fields is studied. • It is shown that this system displays the quenching of tunneling processes. • Our findings provide a control of quantum molecular magnets via terahertz radiation.

  11. Electron tunneling across a tunable potential barrier

    International Nuclear Information System (INIS)

    Mangin, A; Anthore, A; Rocca, M L Della; Boulat, E; Lafarge, P

    2009-01-01

    We present an experiment where the elementary quantum electron tunneling process should be affected by an independent gate voltage parameter. We have realized nanotransistors where the source and drain electrodes are created by electromigration inducing a nanometer sized gap acting as a tunnel barrier. The barrier potential shape is in first approximation considered trapezoidal. The application of a voltage to the gate electrode close to the barrier region can in principle affect the barrier shape. Simulations of the source drain tunnel current as a function of the gate voltage predict modulations as large as one hundred percent. The difficulty of observing the predicted behaviour in our samples might be due to the peculiar geometry of the realized tunnel junction.

  12. Dynamical quenching of tunneling in molecular magnets

    International Nuclear Information System (INIS)

    José Santander, María; Nunez, Alvaro S.; Roldán-Molina, A.; Troncoso, Roberto E.

    2015-01-01

    It is shown that a single molecular magnet placed in a rapidly oscillating magnetic field displays the phenomenon of quenching of tunneling processes. The results open a way to manipulate the quantum states of molecular magnets by means of radiation in the terahertz range. Our analysis separates the time evolution into slow and fast components thereby obtaining an effective theory for the slow dynamics. This effective theory presents quenching of the tunnel effect, in particular, stands out its difference with the so-called coherent destruction of tunneling. We support our prediction with numerical evidence based on an exact solution of Schrödinger's equation. - Highlights: • Single molecular magnets under rapidly oscillating magnetic fields is studied. • It is shown that this system displays the quenching of tunneling processes. • Our findings provide a control of quantum molecular magnets via terahertz radiation

  13. Dielectric Sensors Based on Electromagnetic Energy Tunneling

    Directory of Open Access Journals (Sweden)

    Omar Siddiqui

    2015-03-01

    Full Text Available We show that metallic wires embedded in narrow waveguide bends and channels demonstrate resonance behavior at specific frequencies. The electromagnetic energy at these resonances tunnels through the narrow waveguide channels with almost no propagation losses. Under the tunneling behavior, high-intensity electromagnetic fields are produced in the vicinity of the metallic wires. These intense field resonances can be exploited to build highly sensitive dielectric sensors. The sensor operation is explained with the help of full-wave simulations. A practical setup consisting of a 3D waveguide bend is presented to experimentally observe the tunneling phenomenon. The tunneling frequency is predicted by determining the input impedance minima through a variational formula based on the Green function of a probe-excited parallel plate waveguide.

  14. Thermodynamics of phonon-modulated tunneling centers

    International Nuclear Information System (INIS)

    Junker, W.; Wagner, M.

    1989-01-01

    In recent years tunneling centers have frequently been used to explain the unusual thermodynamic properties of disordered materials; in these approaches, however, the effect of the tunneling-phonon interaction is neglected. The present study considers the archetype model of phono-assisted tunneling, which is well known from other areas of tunneling physics (quantum diffusion, etc.). It is shown that the full thermodynamic information can be rigorously extracted from a single Green function. An extended factorization procedure beyond Hartree-Fock is introduced, which is checked by sum rules as well as by exact Goldberger-Adams expansions. The phonon-modulated internal energy and specific heat are calculated for different power-law coupling setups

  15. Engineering a de Novo Transport Tunnel

    Czech Academy of Sciences Publication Activity Database

    Březovský, J.; Babková, P.; Degtjarik, O.; Fořtová, A.; Gora, A.; Iermak, I.; Řezáčová, Pavlína; Dvořák, P.; Kutá Smatanová, I.; Prokop, Z.; Chaloupková, R.; Damborský, J.

    2016-01-01

    Roč. 6, č. 11 (2016), s. 7597-7610 ISSN 2155-5435 Institutional support: RVO:61388963 Keywords : transport tunnel * protein engineering * protein design * activity * specificity Subject RIV: CE - Biochemistry Impact factor: 10.614, year: 2016

  16. Electroluminescence from graphene excited by electron tunneling

    International Nuclear Information System (INIS)

    Beams, Ryan; Bharadwaj, Palash; Novotny, Lukas

    2014-01-01

    We use low-energy electron tunneling to excite electroluminescence in single layer graphene. Electrons are injected locally using a scanning tunneling microscope and the luminescence is analyzed using a wide-angle optical imaging system. The luminescence can be switched on and off by inverting the tip–sample bias voltage. The observed luminescence is explained in terms of a hot luminescence mechanism. (paper)

  17. General risks for tunnelling projects: An overview

    Science.gov (United States)

    Siang, Lee Yong; Ghazali, Farid E. Mohamed; Zainun, Noor Yasmin; Ali, Roslinda

    2017-10-01

    Tunnels are indispensable when installing new infrastructure as well as when enhancing the quality of existing urban living due to their unique characteristics and potential applications. Over the past few decades, there has been a significant increase in the building of tunnels, world-wide. Tunnelling projects are complex endeavors, and risk assessment for tunnelling projects is likewise a complex process. Risk events are often interrelated. Occurrence of a technical risk usually carries cost and schedule consequences. Schedule risks typically impact cost escalation and project overhead. One must carefully consider the likelihood of a risk's occurrence and its impact in the context of a specific set of project conditions and circumstances. A project's goals, organization, and environment impacts in the context of a specific set of project conditions and circumstances. Some projects are primarily schedule driven; other projects are primarily cost or quality driven. Whether a specific risk event is perceived fundamentally as a cost risk or a schedule risk is governed by the project-specific context. Many researchers have pointed out the significance of recognition and control of the complexity, and risks of tunnelling projects. Although all general information on a project such as estimated duration, estimated cost, and stakeholders can be obtained, it is still quite difficult to accurately understand, predict and control the overall situation and development trends of the project, leading to the risks of tunnelling projects. This paper reviews all the key risks for tunnelling projects from several case studies that have been carried out by other researchers. These risks have been identified and reviewed in this paper. As a result, the current risk management plan in tunnelling projects can be enhanced by including all these reviewed risks as key information.

  18. Automatic control of cryogenic wind tunnels

    Science.gov (United States)

    Balakrishna, S.

    1989-01-01

    Inadequate Reynolds number similarity in testing of scaled models affects the quality of aerodynamic data from wind tunnels. This is due to scale effects of boundary-layer shock wave interaction which is likely to be severe at transonic speeds. The idea of operation of wind tunnels using test gas cooled to cryogenic temperatures has yielded a quantrum jump in the ability to realize full scale Reynolds number flow similarity in small transonic tunnels. In such tunnels, the basic flow control problem consists of obtaining and maintaining the desired test section flow parameters. Mach number, Reynolds number, and dynamic pressure are the three flow parameters that are usually required to be kept constant during the period of model aerodynamic data acquisition. The series of activity involved in modeling, control law development, mechanization of the control laws on a microcomputer, and the performance of a globally stable automatic control system for the 0.3-m Transonic Cryogenic Tunnel (TCT) are discussed. A lumped multi-variable nonlinear dynamic model of the cryogenic tunnel, generation of a set of linear control laws for small perturbation, and nonlinear control strategy for large set point changes including tunnel trajectory control are described. The details of mechanization of the control laws on a 16 bit microcomputer system, the software features, operator interface, the display and safety are discussed. The controller is shown to provide globally stable and reliable temperature control to + or - 0.2 K, pressure to + or - 0.07 psi and Mach number to + or - 0.002 of the set point value. This performance is obtained both during large set point commands as for a tunnel cooldown, and during aerodynamic data acquisition with intrusive activity like geometrical changes in the test section such as angle of attack changes, drag rake movements, wall adaptation and sidewall boundary-layer removal. Feasibility of the use of an automatic Reynolds number control mode with

  19. Conservative therapeutic management of carpal tunnel syndrome

    Directory of Open Access Journals (Sweden)

    Roberto Sérgio Martins

    Full Text Available ABSTRACT Carpal tunnel syndrome is the most prevalent nerve compression and can be clinically or surgically treated. In most cases, the first therapeutic alternative is conservative treatment but there is still much controversy regarding the most effective modality of this treatment. In this study, we critically evaluated the options of conservative treatment for carpal tunnel syndrome, aiming to guide the reader through the conventional options used in this therapy.

  20. Spin Tunneling in a Rotating Nanomagnet

    Science.gov (United States)

    O'Keeffe, Michael; Chudnovsky, Eugene; Lehman College Theoretical Condensed Matter Physics Team

    2011-03-01

    We study spin tunneling in a magnetic nanoparticle with biaxial anisotropy that is free to rotate about its anisotropy axis. Exact instanton of the coupled equations of motion is found that connects degenerate classical energy minima. We show that mechanical freedom of the particle renormalizes magnetic anisotropy and increases the tunnel splitting. M. F. O'Keeffe and E. M. Chudnovsky, cond-mat, arXiv:1011.3134.

  1. The temperature in Hawking radiation as tunneling

    International Nuclear Information System (INIS)

    Zhang Baocheng; Cai Qingyu; Zhan Mingsheng

    2009-01-01

    The quasi-classical method of deriving Hawking radiation under the consideration of canonical invariance is investigated. We find that the horizon should be regarded as a two-way barrier and the ingoing amplitude should be calculated according to the negative energy particles tunneling into the black hole because of the whole space-time interchange and thus the standard Hawking temperature is recovered. We also discuss the advantage of the Painleve coordinates in Hawking radiation as tunneling

  2. Work on a transfer tunnel access shaft

    CERN Multimedia

    Laurent Guiraud

    2000-01-01

    Civil engineers work on one of the access shafts from the SPS to the LHC transfer tunnel, which will allow components and equipment to be lowered directly so that minimal transport is required. The transfer tunnel will take a proton beam from the SPS pre-accelerator and inject it into the clockwise circulating ring in the LHC where the beam will be accelerated to a final energy of 7 TeV.

  3. The effect of asymmetry on resonant tunneling

    International Nuclear Information System (INIS)

    Garcia-Calderon, G.

    1986-07-01

    Resonant tunneling experiments on multibarrier coupled heterostructures probe the quasistationary nature of the states of the corresponding one dimensional potential. This work considers the effect of asymmetric one dimensional multibarrier potentials on resonant tunneling. It is shown, by using the properties of the propagator of the system, that this effect may lead to novel resonance phenomena and affects the lifetime of the quasistationary states of the system. The above considerations are illustrated by a simple analytical solvable model. (author)

  4. Reliability of IP Tunnels in Military Networks

    Directory of Open Access Journals (Sweden)

    Pólkowski Marcin

    2016-10-01

    Full Text Available The military networks, contrary to commercial ones, require standards which provide the highest level of security and reliability. The process to assuring redundancy of the main connections through applying various protocols and transmission media causes problem with time needed to re-establish virtual tunnels between different locations in case of damaged link. This article compares reliability of different IP (Internet Protocol tunnels, which were implemented on military network devices.

  5. Effects of neglecting carrier tunneling on electrostatic potential in calculating direct tunneling gate current in deep submicron MOSFETs

    OpenAIRE

    Hakim, MMA; Haque, A

    2002-01-01

    We investigate the validity of the assumption of neglecting carrier tunneling effects on self-consistent electrostatic potential in calculating direct tunneling gate current in deep submicron MOSFETs. Comparison between simulated and experimental results shows that for accurate modeling of direct tunneling current, tunneling effects on potential profile need to be considered. The relative error in gate current due to neglecting carrier tunneling is higher at higher gate voltages and increases...

  6. Hoosac tunnel geothermal heat source. Final report

    Energy Technology Data Exchange (ETDEWEB)

    1982-06-10

    The Hoosac Rail Tunnel has been analyzed as a central element in a district heating system for the City of North Adams. The tunnel has been viewed as a collector of the earth's geothermal heat and a seasonal heat storage facility with heat piped to the tunnel in summer from existing facilities at a distance. Heated fluid would be transported in winter from the tunnel to users who would boost the temperature with individual heat pumps. It was concluded the tunnel is a poor source of geothermal heat. The maximum extractable energy is only 2200 million BTU (20000 gallons of oil) at 58/sup 0/F. The tunnel is a poor heat storage facility. The rock conductivity is so high that 75% of the heat injected would escape into the mountain before it could be recaptured for use. A low temperature system, with individual heat pumps for temperature boost could be economically attractive if a low cost fuel (byproduct, solid waste, cogeneration) or a cost effective seasonal heat storage were available.

  7. Projection operator method for collective tunneling transitions

    International Nuclear Information System (INIS)

    Kohmura, Toshitake; Ohta, Hirofumi; Hashimoto, Yukio; Maruyama, Masahiro

    2002-01-01

    Collective tunneling transitions take place in the case that a system has two nearly degenerate ground states with a slight energy splitting, which provides the time scale of the tunneling. The Liouville equation determines the evolution of the density matrix, while the Schroedinger equation determines that of a state. The Liouville equation seems to be more powerful for calculating accurately the energy splitting of two nearly degenerate eigenstates. However, no method to exactly solve the Liouville eigenvalue equation has been established. The usual projection operator method for the Liouville equation is not feasible. We analytically solve the Liouville evolution equation for nuclear collective tunneling from one Hartree minimum to another, proposing a simple and solvable model Hamiltonian for the transition. We derive an analytical expression for the splitting of energy eigenvalues from a spectral function of the Liouville evolution using a half-projected operator method. A full-order analytical expression for the energy splitting is obtained. We define the collective tunneling path of a microscopic Hamiltonian for collective tunneling, projecting the nuclear ground states onto n-particle n-hole state spaces. It is argued that the collective tunneling path sector of a microscopic Hamiltonian can be transformed into the present solvable model Hamiltonian. (author)

  8. Quantum tunneling of magnetization in solids

    International Nuclear Information System (INIS)

    Stamp, P.C.E.; Barbara, B.

    1992-01-01

    Magnetic solids should, under certain circumstances, show macroscopic quantum behavior, in which coherence exists between completely distinct magnetization states, each involving a very large number of spins (∼10 12 spins). This article reviews the recent work in this field, concentrating particularly on macroscopic quantum tunneling (MQT) of magnetization. The two main phenomena discussed are the tunneling of magnetization in single-domain particles or grains (in which some 10 3 - 10 4 spins rotate together through an energy barrier), and the tunneling of domain walls in films or in bulk magnets; where walls containing ∼10 10 spins may tunnel off a pinning potential, or from one pinning center to another. Some attention is also given to the quantum nucleation of magnetization reversal in a bulk magnet, and to the quantum motion of other magnetic solitons (such as vortices). After a thorough analysis of the basic grain and wall tunneling phenomena, the authors continue on to a discussion of the various dissipative or decoherence mechanisms, which destroy the phase correlations involved in tunneling. The coupling of grain magnetization to phonons, photons, and electrons is shown to have little consequence for weakly-conducting or insulating grains. Domain walls couple to these and also to magnons and impurities or defects; the 3rd order coupling to magnons can have serious effects, but if one uses pure insulators at low temperatures, these can also be ignored

  9. Outcome of open carpal tunnel release surgery

    International Nuclear Information System (INIS)

    Khan, A.A.; Ali, H.; Muhammad, G.; Gul, N.; Zardan, K.K.; Mushtaq, M.; Ali, S.; Bhatti, S.N.; Ali, K.; Rashid, B.; Saboor, A.

    2015-01-01

    Background: Carpel tunnel syndrome is a common compression neuropathy of the median nerve causing pain, numbness and functional dysfunction of the hand. Among the available treatments, surgical release of the nerve is the most effective and acceptable treatment option. The aim of this study was to see the outcomes of surgical release of carpel tunnel using open technique. Method: This descriptive case series was conducted at the Department of neurosurgery, Ayub Teaching Hospital Abbottabad from April 2013 to March 2014. One hundred consecutive patients with carpel tunnel syndrome were included who underwent open carpel tunnel release surgery. They were followed up at 1, 3 and 6 months. Residual pain, numbness and functional improvement of the hand were the main outcome measures. Results: Out of 100 patients, 19 were males. The age ranged from 32 to 50 years with a mean of 39.29±3.99 years. The duration of symptoms was from 5 to 24 months. In the entire series patient functional outcome and satisfaction was 82 percentage at 1 month, 94 percentage at 3 months and 97 percentage at 6 months. 18 percentage patient had residual pain at 1 month post-operative follow-up, 6percentage at 3 months and 3 percentage at 6 month follow-up. Conclusion: Open carpel tunnel release surgery is an effective procedure for compression neuropathy of the median nerve. It should be offered to all patients with moderate to severe pain and functional disability related to carpel tunnel syndrome. (author)

  10. Postoperative Pain Management after Carpal Tunnel Syndrome Surgical Treatment: Comparing Practice with Guidelines.

    Science.gov (United States)

    Utrobičić, Ivan; Utrobičić, Frane; Prološčić, Ivona; Utrobičić, Toni; Jerić, Milka; Jeličić Kadić, Antonia; Puljak, Livia

    2017-09-01

    The management of postoperative pain after carpal tunnel syndrome surgical treatment at a tertiary hospital was analyzed and compared with the guidelines for perioperative pain management. This retrospective study included 579 patients operated on for carpal tunnel syndrome at the Split University Hospital Center in Split, Croatia. The following key data were collected from patient medical records: age, gender, type and dosage of premedication, type and dosage of anesthesia, type and dosage of postoperative analgesia per each postoperative day. The procedures related to perioperative pain were analyzed and compared with the current guidelines for perioperative acute pain management. Study results showed that 99.6% of patients with carpal tunnel syndrome were operated under local anesthesia, of which 2.9% also received sedation. Analgesics were prescribed to 45% of patients after surgery, and according to patient charts, 39% of patients actually received postoperative analgesic(s). Generally, postoperative pain was treated on the fi rst postoperative day, mostly with nonsteroidal anti-inflammatory drugs. Only two patients received weak opioids for postoperative pain. Many recommendations from the guidelines for perioperative acute pain management were not followed. In conclusion, the guidelines should be followed and appropriate interventions used to improve postoperative pain management.

  11. Organic tunnel field effect transistors

    KAUST Repository

    Tietze, Max Lutz

    2017-06-29

    Various examples are provided for organic tunnel field effect transistors (OTFET), and methods thereof. In one example, an OTFET includes a first intrinsic layer (i-layer) of organic semiconductor material disposed over a gate insulating layer; source (or drain) contact stacks disposed on portions of the first i-layer; a second i-layer of organic semiconductor material disposed on the first i-layer surrounding the source (or drain) contact stacks; an n-doped organic semiconductor layer disposed on the second i-layer; and a drain (or source) contact layer disposed on the n-doped organic semiconductor layer. The source (or drain) contact stacks can include a p-doped injection layer, a source (or drain) contact layer, and a contact insulating layer. In another example, a method includes disposing a first i-layer over a gate insulating layer; forming source or drain contact stacks; and disposing a second i-layer, an n-doped organic semiconductor layer, and a drain or source contact.

  12. Le LHC, un tunnel cosmique

    CERN Multimedia

    CERN. Geneva

    2009-01-01

    Et si la lumière au bout du tunnel du LHC était cosmique ? En d’autres termes, qu’est-ce que le LHC peut nous apporter dans la connaissance de l’Univers ? Car la montée en énergie des accélérateurs de particules nous permet de mieux appréhender l’univers primordial, chaud et dense. Mais dans quel sens dit-on que le LHC reproduit des conditions proches du Big bang ? Quelles informations nous apporte-t-il sur le contenu de l’Univers ? La matière noire est-elle détectable au LHC ? L’énergie noire ? Pourquoi l’antimatière accumulée au CERN est-elle si rare dans l’Univers ? Et si le CERN a bâti sa réputation sur l’exploration des forces faibles et fortes qui opèrent au sein des atomes et de leurs noyaux, est-ce que le LHC peut nous apporter des informations sur la force gravitationnelle qui gouverne l’évolution cosmique ? Depuis une trentaine d’années, notre compréhension de l’univers dans ses plus grandes dimensions et l’appréhension de son comportement aux plus peti...

  13. Coherence in Magnetic Quantum Tunneling

    Science.gov (United States)

    Fernandez, Julio F.

    2001-03-01

    Crystals of single molecule magnets such as Mn_12 and Fe8 behave at low temperatures as a collection of independent spins. Magnetic anisotropy barriers slow down spin-flip processes. Their rate Γ becomes temperature independent at sufficiently low temperature. Quantum tunneling (QT) accounts for this behavior. Currently, spin QT in Mn_12 and Fe8 is assumed to proceed as an incoherent sum of small probability increments that occur whenever a bias field h(t) (arising from hyperfine interactions with nuclear spins) that varies with time t becomes sufficiently small, as in Landau-Zener transitions. Within a two-state model, we study the behavior of a suitably defined coherence time τ_φ and compare it with the correlation time τh for h(t). It turns out that τ_φ >τ_h, when τ_hδ h < hbar, where δ h is the rms deviation of h. We show what effect such coherence has on Γ. Its dependence on a static longitudinal applied field Hz is drastically affected. There is however no effect if the field is swept through resonance.

  14. Tunneling and Transport in Nanowires

    International Nuclear Information System (INIS)

    Goldman, Allen M.

    2016-01-01

    The goal of this program was to study new physical phenomena that might be relevant to the performance of conductive devices and circuits of the smallest realizable feature sizes possible using physical rather than biological techniques. Although the initial scientific work supported involved the use of scanning tunneling microscopy and spectroscopy to ascertain the statistics of the energy level distribution of randomly sized and randomly shaped quantum dots, or nano-crystals, the main focus was on the investigation of selected properties, including superconductivity, of conducting and superconducting nanowires prepared using electron-beam-lithography. We discovered a magnetic-field-restoration of superconductivity in out-of-equilibrium nanowires driven resistive by current. This phenomenon was explained by the existence of a state in which dissipation coexisted with nonvanishing superconducting order. We also produced ultra-small superconducting loops to study a predicted anomalous fluxoid quantization, but instead, found a magnetic-field-dependent, high-resistance state, rather than superconductivity. Finally, we developed a simple and controllable nanowire in an induced charged layer near the surface of a masked single-crystal insulator, SrTiO_3. The layer was induced using an electric double layer transistor employing an ionic liquid (IL). The transport properties of the induced nanowire resembled those of collective electronic transport through an array of quantum dots.

  15. Tunneling and Transport in Nanowires

    Energy Technology Data Exchange (ETDEWEB)

    Goldman, Allen M. [Univ. of Minnesota, Minneapolis, MN (United States)

    2016-08-16

    The goal of this program was to study new physical phenomena that might be relevant to the performance of conductive devices and circuits of the smallest realizable feature sizes possible using physical rather than biological techniques. Although the initial scientific work supported involved the use of scanning tunneling microscopy and spectroscopy to ascertain the statistics of the energy level distribution of randomly sized and randomly shaped quantum dots, or nano-crystals, the main focus was on the investigation of selected properties, including superconductivity, of conducting and superconducting nanowires prepared using electron-beam-lithography. We discovered a magnetic-field-restoration of superconductivity in out-of-equilibrium nanowires driven resistive by current. This phenomenon was explained by the existence of a state in which dissipation coexisted with nonvanishing superconducting order. We also produced ultra-small superconducting loops to study a predicted anomalous fluxoid quantization, but instead, found a magnetic-field-dependent, high-resistance state, rather than superconductivity. Finally, we developed a simple and controllable nanowire in an induced charged layer near the surface of a masked single-crystal insulator, SrTiO3. The layer was induced using an electric double layer transistor employing an ionic liquid (IL). The transport properties of the induced nanowire resembled those of collective electronic transport through an array of quantum dots.

  16. Tunnel boring waste test plan

    International Nuclear Information System (INIS)

    Patricio, J.G.

    1984-03-01

    The test plan has been prepared in anticipation of the need to excavate certain repository openings by relying upon mechanical excavation techniques. The test plan proposes that specific technical issues can be resolved and key design parameters defined by excavating openings in basalt near the surface, utilizing a full face tunnel boring machine (TBM). The purpose and objective of this type of testing will define the overall feasibility and attributes of mechanical excavation in basalt. The test plan recognizes that although this technology is generally available for underground construction for some geologic settings, the current state of technology for excavation in basalt is limited and the potential for improvement is considerable. The test plan recommends that it is economically advantageous to conduct additional testing in the laboratory to allow refinement of this plan based on the laboratory results. Thus, this test plan is considered preliminary in nature, with respect to detailed testing recommendations. However, the gross design attributes and resource requirements of a near-surface TBM demonstration are considered to be valid. 15 refs., 7 figs., 3 tabs

  17. Tunnel junctions with multiferroic barriers

    Science.gov (United States)

    Gajek, Martin; Bibes, Manuel; Fusil, Stéphane; Bouzehouane, Karim; Fontcuberta, Josep; Barthélémy, Agnès; Fert, Albert

    2007-04-01

    Multiferroics are singular materials that can exhibit simultaneously electric and magnetic orders. Some are ferroelectric and ferromagnetic and provide the opportunity to encode information in electric polarization and magnetization to obtain four logic states. However, such materials are rare and schemes allowing a simple electrical readout of these states have not been demonstrated in the same device. Here, we show that films of La0.1Bi0.9MnO3 (LBMO) are ferromagnetic and ferroelectric, and retain both ferroic properties down to a thickness of 2nm. We have integrated such ultrathin multiferroic films as barriers in spin-filter-type tunnel junctions that exploit the magnetic and ferroelectric degrees of freedom of LBMO. Whereas ferromagnetism permits read operations reminiscent of magnetic random access memories (MRAM), the electrical switching evokes a ferroelectric RAM write operation. Significantly, our device does not require the destructive ferroelectric readout, and therefore represents an advance over the original four-state memory concept based on multiferroics.

  18. Tunnelling in Soft Soil : Tunnel Boring Machine Operation and Soil Response

    NARCIS (Netherlands)

    Festa, D.; Broere, W.; Bosch, J.W.

    2013-01-01

    Constructing tunnels in soft soil with the use of Tunnel Boring Machines may induce settlements including soil movements ahead of the face, soil relaxation into the tail void, possible heave due to grouting, long lasting consolidation processes, and potentially several other mechanisms. A

  19. Disc Bit Abrasion Parameters in TBM Tunnelling regarded exemplarily for the Gotthard Base Tunnel

    Directory of Open Access Journals (Sweden)

    Edmund a Wax

    2005-11-01

    Full Text Available In this article the author presents Amund Bruland’s empirical approach to determine the disc bit abrasion of TBMs (Tunnel Boring Machines, transforms the respective empirical dependencies into approximated mathematical relations and verifies them exemplarily for the currently constructed Gotthard Base Tunnel.

  20. Quantum dot resonant tunneling diode single photon detector with aluminum oxide aperture defined tunneling area

    DEFF Research Database (Denmark)

    Li, H.W.; Kardynal, Beata; Ellis, D.J.P.

    2008-01-01

    Quantum dot resonant tunneling diode single photon detector with independently defined absorption and sensing areas is demonstrated. The device, in which the tunneling is constricted to an aperture in an insulating layer in the emitter, shows electrical characteristics typical of high quality res...

  1. Spin-polarized tunneling with GaAs tips in scanning tunneling microscopy

    NARCIS (Netherlands)

    Prins, M.W.J.; Jansen, R.; Kempen, van H.

    1996-01-01

    We describe a model as well as experiments on spin-polarized tunneling with the aid of optical spin orientation. This involves tunnel junctions between a magnetic material and gallium arsenide (GaAs), where the latter is optically excited with circularly polarized light in order to generate

  2. Fabrication of magnetic tunnel junctions with a single-crystalline LiF tunnel barrier

    Science.gov (United States)

    Krishna Narayananellore, Sai; Doko, Naoki; Matsuo, Norihiro; Saito, Hidekazu; Yuasa, Shinji

    2018-04-01

    We fabricated Fe/LiF/Fe magnetic tunnel junctions (MTJs) by molecular beam epitaxy on a MgO(001) substrate, where LiF is an insulating tunnel barrier with the same crystal structure as MgO (rock-salt type). Crystallographical studies such as transmission electron microscopy and nanobeam electron diffraction observations revealed that the LiF tunnel barrier is single-crystalline and has a LiF(001)[100] ∥ bottom Fe(001)[110] crystal orientation, which is constructed in the same manner as MgO(001) on Fe(001). Also, the in-plane lattice mismatch between the LiF tunnel barrier and the Fe bottom electrode was estimated to be small (about 0.5%). Despite such advantages for the tunnel barrier of the MTJ, the observed tunnel magnetoresistance (MR) ratio was low (˜6% at 20 K) and showed a significant decrease with increasing temperature (˜1% at room temperature). The results imply that indirect tunneling and/or thermally excited carriers in the LiF tunnel barrier, in which the current basically is not spin-polarized, play a major role in electrical transport in the MTJ.

  3. Does flexible tunnel drilling affect the femoral tunnel angle measurement after anterior cruciate ligament reconstruction?

    NARCIS (Netherlands)

    Muller, Bart; Hofbauer, Marcus; Atte, Akere; van Dijk, C. Niek; Fu, Freddie H.

    2015-01-01

    To quantify the mean difference in femoral tunnel angle (FTA) as measured on knee radiographs between rigid and flexible tunnel drilling after anatomic anterior cruciate ligament (ACL) reconstruction. Fifty consecutive patients that underwent primary anatomic ACL reconstruction with a single femoral

  4. Does flexible tunnel drilling affect the femoral tunnel angle measurement after anterior cruciate ligament reconstruction?

    Science.gov (United States)

    Muller, Bart; Hofbauer, Marcus; Atte, Akere; van Dijk, C Niek; Fu, Freddie H

    2015-12-01

    To quantify the mean difference in femoral tunnel angle (FTA) as measured on knee radiographs between rigid and flexible tunnel drilling after anatomic anterior cruciate ligament (ACL) reconstruction. Fifty consecutive patients that underwent primary anatomic ACL reconstruction with a single femoral tunnel drilled with a flexible reamer were included in this study. The control group was comprised of 50 patients all of who underwent primary anatomic ACL reconstruction with a single femoral tunnel drilled with a rigid reamer. All femoral tunnels were drilled through a medial portal to ensure anatomic tunnel placement. The FTA was determined from post-operative anterior-to-posterior (AP) radiographs by two independent observers. A 5° difference between the two mean FTA was considered clinically significant. The average FTA, when drilled with a rigid reamer, was 42.0° ± 7.2°. Drilling with a flexible reamer resulted in a mean FTA of 44.7° ± 7.0°. The mean difference of 2.7° was not statistically significant. The intraclass correlation coefficient for inter-tester reliability was 0.895. The FTA can be reliably determined from post-operative AP radiographs and provides a useful and reproducible metric for characterizing femoral tunnel position after both rigid and flexible femoral tunnel drilling. This has implications for post-operative evaluation and preoperative treatment planning for ACL revision surgery. IV.

  5. Acute Pancreatitis

    DEFF Research Database (Denmark)

    Bertilsson, Sara; Håkansson, Anders; Kalaitzakis, Evangelos

    2017-01-01

    Aims: We aimed to evaluate the potential relation between the incidence of (alcoholic and non-alcoholic) acute pancreatitis (AP) and alcohol consumption in the general population, and whether the occurrence of AP shows any seasonal variation, particularly in relation to periods with expected...... consumption in the general population do not appear to be related to changes in the incidence of AP and there are no significant seasonal differences in the occurrence of AP in Sweden. Short summary: The incidence of acute pancreatitis (AP) is increasing, and alcohol is still recognized as one of the most...

  6. Scanning tunneling microscopic images and scanning tunneling spectra for coupled rectangular quantum corrals

    International Nuclear Information System (INIS)

    Mitsuoka, Shigenori; Tamura, Akira

    2011-01-01

    Assuming that an electron confined by double δ-function barriers lies in a quasi-stationary state, we derived eigenstates and eigenenergies of the electron. Such an electron has a complex eigenenergy, and the imaginary part naturally leads to the lifetime of the electron associated with tunneling through barriers. We applied this point of view to the electron confined in a rectangular quantum corral (QC) on a noble metal surface, and obtained scanning tunneling microscopic images and a scanning tunneling spectrum consistent with experimental ones. We investigated the electron states confined in coupled QCs and obtained the coupled states constructed with bonding and anti-bonding states. Using those energy levels and wavefunctions we specified scanning tunneling microscope (STM) images and scanning tunneling spectra (STS) for the doubly and triply coupled QCs. In addition we pointed out the feature of resonant electron states associated with the same QCs at both ends of the triply coupled QCs.

  7. Development of the tunneling junction simulation environment for scanning tunneling microscope evaluation

    International Nuclear Information System (INIS)

    Gajewski, Krzysztof; Piasecki, Tomasz; Kopiec, Daniel; Gotszalk, Teodor

    2017-01-01

    Proper configuration of scanning tunneling microscope electronics plays an important role in the atomic scale resolution surface imaging. Device evaluation in the tunneling contact between scanning tip and sample may be prone to the surface quality or mechanical disturbances. Thus the use of tunneling junction simulator makes electronics testing more reliable and increases its repeatability. Here, we present the theoretical background enabling the proper selection of electronic components circuitry used as a tunneling junction simulator. We also show how to simulate mechanics related to the piezoelectric scanner, which is applied in real experiments. Practical use of the proposed simulator and its application in metrological characterization of the developed scanning tunneling microscope is also shown. (paper)

  8. Electrical installations of the Channel tunnel; Installations electriques du Tunnel sous la Manche

    Energy Technology Data Exchange (ETDEWEB)

    Kersabiec, G. de [Eurotunnel, Folkestone (United Kingdom)

    2002-08-01

    Like an underground factory, the railway and auxiliary equipments of the Channel tunnel between France and UK, need a reliable and redundant power supply with a high quality maintenance. This article presents: the design criteria of the power distribution systems, the installation itself and the organisation of its exploitation: 1 - transportation system of the Channel tunnel (loads to supply, exploitation imperatives, fundamental criteria); 2 - external power sources (connection to the UK and French grids, values used by the national grids); 3 - exploitation criteria, tunnel design; 4 - description (main UK and French power stations, 25 kV traction network, 21 kV distribution network, tunnels, lighting in railway tunnels, supply of terminals, earthing network); 5 - exploitation; 6 - maintenance and quality. (J.S.)

  9. Design of Intelligent Power Supply System for Expressway Tunnel

    Science.gov (United States)

    Wang, Li; Li, Yutong; Lin, Zimian

    2018-01-01

    Tunnel lighting program is one of the key points of tunnel infrastructure construction. As tunnels tend to handle remote locations, power supply line construction generally has been having the distance, investment, high cost characteristics. To solve this problem, we propose a green, environmentally friendly, energy-efficient lighting system. This program uses the piston-wind which cars within tunnel produce as the power and combines with solar energy, physical lighting to achieve it, which solves the problem of difficult and high cost of highway tunnel section, and provides new ideas for the future construction of tunnel power supply.

  10. Unified time analysis of photon and particle tunnelling

    International Nuclear Information System (INIS)

    Olkhovsky, Vladislav S.; Recami, Erasmo; Jakiel, Jacek

    2001-07-01

    A unified approach to the time analysis of tunnelling of nonrelativistic particles is presented, in which Time is regarded as a quantum-mechanical observable, canonically conjugated to Energy. The validity of the Hartman effect (independence of the Tunnelling Time of the opaque barrier width, with superluminal group velocities as a consequence) is verified for all the known expressions of the mean tunnelling time. Moreover, the analogy between particle and photon tunnelling is suitably exploited. On the basic of such an analogy, an explanation of some recent microwave and optics experimental results on tunnelling time is proposed. Attention is devoted to some aspects of the causality problem for particle and photon tunnelling. (author)

  11. Influence of knee flexion angle and transverse drill angle on creation of femoral tunnels in double-bundle anterior cruciate ligament reconstruction using the transportal technique: Three-dimensional computed tomography simulation analysis.

    Science.gov (United States)

    Choi, Chong Hyuk; Kim, Sung-Jae; Chun, Yong-Min; Kim, Sung-Hwan; Lee, Su-Keon; Eom, Nam-Kyu; Jung, Min

    2018-01-01

    The purpose of this study was to find appropriate flexion angle and transverse drill angle for optimal femoral tunnels of anteromedial (AM) bundle and posterolateral (PL) bundle in double-bundle ACL reconstruction using transportal technique. Thirty three-dimensional knee models were reconstructed. Knee flexion angles were altered from 100° to 130° at intervals of 10°. Maximum transverse drill angle (MTA), MTA minus 10° and 20° were set up. Twelve different tunnels were determined by four flexion angles and three transverse drill angles for each bundle. Tunnel length, wall breakage, inter-tunnel communication and graft-bending angle were assessed. Mean tunnel length of AM bundle was >30mm at 120° and 130° of flexion in all transverse drill angles. Mean tunnel length of PL bundle was >30mm during every condition. There were ≥1 cases of wall breakage except at 120° and 130° of flexion with MTA for AM bundle. There was no case of wall breakage for PL bundle. Considering inter-tunnel gap of >2mm without communication and obtuse graft-bending angle, 120° of flexion and MTA could be recommended as optimal condition for femoral tunnels of AM and PL bundles. Flexion angle and transverse drill angle had combined effect on femoral tunnel in double-bundle ACL reconstruction using transportal technique. Achieving flexion angle of 120° and transverse drill angle close to the medial femoral condyle could be recommended as optimal condition for femoral tunnels of AM and PL bundles to avoid insufficient tunnel length, wall breakage, inter-tunnel communication and acute graft-bending angle. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. Particle detection with superconducting tunnel junctions

    International Nuclear Information System (INIS)

    Jany, P.

    1990-08-01

    At the Institute of Experimental Nuclear Physics of the University of Karlsruhe (TH) and at the Institute for Nuclear Physics of the Kernforschungszentrum Karlsruhe we started to produce superconducting tunnel junctions and to investigate them for their suitability as particle detectors. The required facilities for the production of tunnel junctions and the experimental equipments to carry out experiments with them were erected. Experiments are presented in which radiations of different kinds of particles could successfully be measured with the tunnel junctions produced. At first we succeeded in detectioning light pulses of a laser. In experiments with alpha-particles of an energy of 4,6 MeV the alpha-particles were detected with an energy resolution of 1,1%, and it was shown in specific experiments that the phonons originating from the deposition of energy by an alpha-particle in the substrate can be detected with superconducting tunnel junctions at the surface. On that occasion it turned out that the signals could be separated with respect to their point of origin (tunnel junction, contact leads, substrate). Finally X-rays with an energy of 6 keV were detected with an energy resolution of 8% in a test arrangement that makes use of the so-called trapping effect to read out a larger absorber volume. (orig.) [de

  13. Safe design of protective structures of tunnels

    International Nuclear Information System (INIS)

    Farahat, M.A.Z.

    2011-01-01

    This research aims to explain how to use a tunnel, constructed from reinforced concrete, passes under a river to protect some people. The computer code is used (MCNP) (the transfer photon and neutron) at this model for such tunnel which passes under a river to account attenuation of both neutrons and gamma rays passing through the river water, clay, soil and reinforced concrete wall layers ,the last one (thickness 40 cm)constructed the tunnel construction. And to account the dose inside the tunnel, and to account neutron dose, gamma dose, prompt gamma dose, total gamma dose and total (neutron + gamma) dose estimated by μSv/h. At different depths from the earth surface layer depths 100 cm, 250 cm, 500 cm, 750 cm , 1000 cm, 1300 cm, 1700 cm, 1900 cm, 2020 cm, 2500 cm). And then account these doses for three cases which are a nuclear bomb its intensity 20 kt, another bomb its intensity 100 kt, and the last one its intensity is 1000 kt. This research aims to account the required safe depth to protect some people in this tunnel, passing under a river from the dangerous effects of neutron and gamma rays, emitted from the nuclear bomb.

  14. Unidirectional magnetoelectric-field multiresonant tunneling

    International Nuclear Information System (INIS)

    Kamenetskii, E O; Hollander, E; Joffe, R; Shavit, R

    2015-01-01

    Unidirectional multi-resonant tunneling of the magnetoelectric (ME) field excitations through a subwavelength (regarding the scales of regular electromagnetic radiation) vacuum or isotropic-dielectric regions has been observed in two-port microwave structures having a quasi-2D ferrite disk with magnetic dipolar mode (MDM) oscillations. The excitations manifest themselves as Fano-resonance peaks in the scattering-matrix parameters at the stationary states of the MDM spectrum. The ME near-field excitations are quasimagnetostatic fields ∇-vector × H-vector =0 with non-zero helicity parameter: F=(1/(16π))Im{ E-vector ⋅( ∇-vector × E-vector ) ∗ }. Topological phase properties of ME fields are determined by edge chiral currents of MDM oscillations. We show that while for a given direction of a bias magnetic field (in other words, for a given direction of time), the ME field excitations are considered as ‘forward’ tunneling processes, in the opposite direction of a bias magnetic field (the opposite direction of time), there are ‘backward’ tunneling processes. Unidirectional ME field resonant tunneling is observed due to the distinguishable topology of the ‘forward’ and ‘backward’ ME field excitations. We establish a close connection between the Fano-resonance unidirectional tunneling and the topology of the ME fields in different microwave structures. (paper)

  15. Channel selective tunnelling through a nanographene assembly

    International Nuclear Information System (INIS)

    Wong, H S; Durkan, C; Feng, X; Müllen, K; Chandrasekhar, N

    2012-01-01

    We report selective tunnelling through a nanographene intermolecular tunnel junction achieved via scanning tunnelling microscope tip functionalization with hexa-peri-hexabenzocoronene (HBC) molecules. This leads to an offset in the alignment between the energy levels of the tip and the molecular assembly, resulting in the imaging of a variety of distinct charge density patterns in the HBC assembly, not attainable using a bare metallic tip. Different tunnelling channels can be selected by the application of an electric field in the tunnelling junction, which changes the condition of the HBC on the tip. Density functional theory-based calculations relate the imaged HBC patterns to the calculated molecular orbitals at certain energy levels. These patterns bear a close resemblance to the π-orbital states of the HBC molecule calculated at the relevant energy levels, mainly below the Fermi energy of HBC. This correlation demonstrates the ability of an HBC functionalized tip as regards accessing an energy range that is restricted to the usual operating bias range around the Fermi energy with a normal metallic tip at room temperature. Apart from relating to molecular orbitals, some patterns could also be described in association with the Clar aromatic sextet formula. Our observations may help pave the way towards the possibility of controlling charge transport between organic interfaces. (paper)

  16. New Knowledge of tunneling from photonic experiments

    International Nuclear Information System (INIS)

    Nimtz, G.

    1997-01-01

    Photonic experiments have shown, that the propagation of evanescent (tunneling) modes can proceed at speeds faster than the velocity of light in vacuum (superluminal). The superluminal velocities include signal and energy propagation. The analogy between the classical Helmholtz equation and the quantum mechanical Schroedinger equation was quantitatively proved in classical photonic experiments. The Hartman effect, i.e. the prediction that the tunneling time is independent of the barrier length was for the first time evidenced in a photonic analogous tunneling experiment by Enders and Nimtz. It is also shown, that the resonant state life time is not determined by the barrier traversal time. For electronic tunneling devices it follows, that the quantum mechanical phase time calculations indeed deliver the relevant intrinsic tunneling time and consequently allow to predict the dynamical specification of a device. The present theoretical descriptions of the propagation of evanescent modes is not fully compatible with the experimental situation. Superluminal signal and energy transport has been measured, and this has to be properly analyzed. May the advanced field solutions help to obtain a satisfactory theoretical description of the recent experimental results of the propagation of evanescent modes? (author)

  17. Complex use of heat-exchange tunnels

    Directory of Open Access Journals (Sweden)

    А. Ф. Галкин

    2017-04-01

    Full Text Available The paper presents separate results of complex research (experimental and theoretical on the application of heat-exchange tunnels – in frozen rocks, among other things – as underground constructions serving two purposes. It is proposed to use heat-exchange tunnels as a separate multi-functional module, which under normal conditions will be used to set standards of heat regime parameters in the mines, and in emergency situations, natural or man-made, will serve as a protective structure to shelter mine workers. Heat-exchange modules can be made from mined-out or specially constructed tunnels. Economic analysis shows that the use of such multi-functional modules does not increase operation and maintenance costs, but enhances safety of mining operations and reliability in case of emergency situations. There are numerous theoretic and experimental investigations in the field of complex use of mining tunnels, which allows to develop regulatory design documents on their basis. Experience of practical application of heat-exchange tunnels has been assessed from the position of regulating heat regime in the mines.

  18. Tunnel Ventilation Control Using Reinforcement Learning Methodology

    Science.gov (United States)

    Chu, Baeksuk; Kim, Dongnam; Hong, Daehie; Park, Jooyoung; Chung, Jin Taek; Kim, Tae-Hyung

    The main purpose of tunnel ventilation system is to maintain CO pollutant concentration and VI (visibility index) under an adequate level to provide drivers with comfortable and safe driving environment. Moreover, it is necessary to minimize power consumption used to operate ventilation system. To achieve the objectives, the control algorithm used in this research is reinforcement learning (RL) method. RL is a goal-directed learning of a mapping from situations to actions without relying on exemplary supervision or complete models of the environment. The goal of RL is to maximize a reward which is an evaluative feedback from the environment. In the process of constructing the reward of the tunnel ventilation system, two objectives listed above are included, that is, maintaining an adequate level of pollutants and minimizing power consumption. RL algorithm based on actor-critic architecture and gradient-following algorithm is adopted to the tunnel ventilation system. The simulations results performed with real data collected from existing tunnel ventilation system and real experimental verification are provided in this paper. It is confirmed that with the suggested controller, the pollutant level inside the tunnel was well maintained under allowable limit and the performance of energy consumption was improved compared to conventional control scheme.

  19. Extruded Tunnel Lining System : Phase 1. Conceptual Design and Feasibility Testing.

    Science.gov (United States)

    1979-09-01

    The Extruded Tunnel Lining System (ETLS) has been conceived as a means of continuously placing the final concrete tunnel lining directly behind a tunnel boring machine. The system will shorten the time required to excavate and line a tunnel section, ...

  20. DNS Tunneling Detection Method Based on Multilabel Support Vector Machine

    Directory of Open Access Journals (Sweden)

    Ahmed Almusawi

    2018-01-01

    Full Text Available DNS tunneling is a method used by malicious users who intend to bypass the firewall to send or receive commands and data. This has a significant impact on revealing or releasing classified information. Several researchers have examined the use of machine learning in terms of detecting DNS tunneling. However, these studies have treated the problem of DNS tunneling as a binary classification where the class label is either legitimate or tunnel. In fact, there are different types of DNS tunneling such as FTP-DNS tunneling, HTTP-DNS tunneling, HTTPS-DNS tunneling, and POP3-DNS tunneling. Therefore, there is a vital demand to not only detect the DNS tunneling but rather classify such tunnel. This study aims to propose a multilabel support vector machine in order to detect and classify the DNS tunneling. The proposed method has been evaluated using a benchmark dataset that contains numerous DNS queries and is compared with a multilabel Bayesian classifier based on the number of corrected classified DNS tunneling instances. Experimental results demonstrate the efficacy of the proposed SVM classification method by obtaining an f-measure of 0.80.

  1. Atmospheric diffusion wind tunnel with automatic measurement

    Energy Technology Data Exchange (ETDEWEB)

    Maki, S; Sakai, J; Murata, E

    1974-01-01

    A wind tunnel which permits estimates of atmospheric diffusion is described. Smoke from power plant smoke stacks, for example, can be simulated and traced to determine the manner of diffusion in the air as well as the grade of dilution. The wind tunnel is also capable of temperature controlled diffusion tests in which temperature distribution inside the wind tunnel is controlled. A minimum wind velocity of 10 cm can be obtained with accuracy within plus or minus 0.05 percent using a controlled direct current motor; diffusion tests are often made at low wind velocity. Fully automatic measurements can be obtained by using a minicomputer so that the operation and reading of the measuring instruments can be remotely controlled from the measuring chamber. (Air Pollut. Abstr.)

  2. Chiral tunneling in a twisted graphene bilayer.

    Science.gov (United States)

    He, Wen-Yu; Chu, Zhao-Dong; He, Lin

    2013-08-09

    The perfect transmission in a graphene monolayer and the perfect reflection in a Bernal graphene bilayer for electrons incident in the normal direction of a potential barrier are viewed as two incarnations of the Klein paradox. Here we show a new and unique incarnation of the Klein paradox. Owing to the different chiralities of the quasiparticles involved, the chiral fermions in a twisted graphene bilayer show an adjustable probability of chiral tunneling for normal incidence: they can be changed from perfect tunneling to partial or perfect reflection, or vice versa, by controlling either the height of the barrier or the incident energy. As well as addressing basic physics about how the chiral fermions with different chiralities tunnel through a barrier, our results provide a facile route to tune the electronic properties of the twisted graphene bilayer.

  3. Scanning Tunneling Spectroscope Use in Electrocatalysis Testing

    Science.gov (United States)

    Knutsen, Turid

    2010-01-01

    The relationship between the electrocatalytic properties of an electrode and its ability to transfer electrons between the electrode and a metallic tip in a scanning tunneling microscope (STM) is investigated. The alkaline oxygen evolution reaction (OER) was used as a test reaction with four different metallic glasses, Ni78Si8B14, Ni70Mo20Si5B5, Ni58Co20Si10B12, and Ni25Co50Si15B10, as electrodes. The electrocatalytic properties of the electrodes were determined. The electrode surfaces were then investigated with an STM. A clear relationship between the catalytic activity of an electrode toward the OER and its tunneling characteristics was found. The use of a scanning tunneling spectroscope (STS) in electrocatalytic testing may increase the efficiency of the optimization of electrochemical processes.

  4. Scanning Tunneling Spectroscope Use in Electrocatalysis Testing

    Directory of Open Access Journals (Sweden)

    Turid Knutsen

    2010-06-01

    Full Text Available The relationship between the electrocatalytic properties of an electrode and its ability to transfer electrons between the electrode and a metallic tip in a scanning tunneling microscope (STM is investigated. The alkaline oxygen evolution reaction (OER was used as a test reaction with four different metallic glasses, Ni78Si8B14, Ni70Mo20Si5B5, Ni58Co20Si10B12, and Ni25Co50Si15B10, as electrodes. The electrocatalytic properties of the electrodes were determined. The electrode surfaces were then investigated with an STM. A clear relationship between the catalytic activity of an electrode toward the OER and its tunneling characteristics was found. The use of a scanning tunneling spectroscope (STS in electrocatalytic testing may increase the efficiency of the optimization of electrochemical processes.

  5. Electronic thermometry in tunable tunnel junction

    Science.gov (United States)

    Maksymovych, Petro

    2016-03-15

    A tunable tunnel junction thermometry circuit includes a variable width tunnel junction between a test object and a probe. The junction width is varied and a change in thermovoltage across the junction with respect to the change in distance across the junction is determined. Also, a change in biased current with respect to a change in distance across the junction is determined. A temperature gradient across the junction is determined based on a mathematical relationship between the temperature gradient, the change in thermovoltage with respect to distance and the change in biased current with respect to distance. Thermovoltage may be measured by nullifying a thermoelectric tunneling current with an applied voltage supply level. A piezoelectric actuator may modulate the probe, and thus the junction width, to vary thermovoltage and biased current across the junction. Lock-in amplifiers measure the derivatives of the thermovoltage and biased current modulated by varying junction width.

  6. Qubit dephasing due to quasiparticle tunneling

    Energy Technology Data Exchange (ETDEWEB)

    Zanker, Sebastian; Marthaler, Michael; Schoen, Gerd [Institut fuer Theoretische Festkoerperphysik, Karlsruhe Institute of Technology, D-76128 Karlsruhe (Germany)

    2015-07-01

    We study dephasing of a superconducting qubit due to quasiparticle tunneling through a Josephson junction. While qubit decay due to tunneling processes is well understood within a golden rule approximation, pure dephasing due to BCS quasiparticles gives rise to a divergent golden rule rate. We calculate qubit dephasing due to quasiparticle tunneling beyond lowest order approximation in coupling between qubit and quasiparticles. Summing up a certain class of diagrams we show that qubit dephasing due to purely longitudinal coupling to quasiparticles leads to dephasing ∝ exp(-x(t)) where x(t) ∝ t{sup 3/2} for short time scales and x(t) ∝ tlog(t) for long time scales.

  7. Phonon tunneling through a double barrier system

    International Nuclear Information System (INIS)

    Villegas, Diosdado; León-Pérez, Fernando de; Pérez-Álvarez, R.; Arriaga, J.

    2015-01-01

    The tunneling of optical and acoustic phonons at normal incidence on a double-barrier is studied in this paper. Transmission coefficients and resonance conditions are derived theoretically under the assumption that the long-wavelength approximation is valid. It is shown that the behavior of the transmission coefficients for the symmetric double barrier has a Lorentzian form close to resonant frequencies and that Breit–Wigner's formula have a general validity in one-dimensional phonon tunneling. Authors also study the so-called generalized Hartman effect in the tunneling of long-wavelength phonons and show that this effect is a numerical artifact resulting from taking the opaque limit before exploring the variation with a finite barrier width. This study could be useful for the design of acoustic devices

  8. Positioning systems for underground tunnel environments

    CERN Document Server

    Leite Pereira, Fernando; Theis, Christian

    In the last years the world has witnessed a remarkable change in the computing concept by entering the mobile era. Incredibly powerful smartphones have proliferated at stunning pace and tablet computers are capable of running demanding applications and meet new business requirements. Being wireless, localization has become crucial not only to serve individuals but also help companies in industrial and safety processes. In the context of the Radiation Protection group at CERN, automatic localization, besides allowing to find people, would help improving the radiation surveys performed regularly along the accelerator tunnels. The research presented in this thesis attempts to answer questions relatively to the viability of localization in a harsh conditions tunnel: “Is localization in a very long tunnel possible, meeting its restrictions and without incurring prohibitive costs and infrastructure?”, “Can one achieve meter-level accuracy with GSM deployed over leaky-feeder?”, “Is it possible to prototype...

  9. Silicon spintronics with ferromagnetic tunnel devices

    International Nuclear Information System (INIS)

    Jansen, R; Sharma, S; Dash, S P; Min, B C

    2012-01-01

    In silicon spintronics, the unique qualities of ferromagnetic materials are combined with those of silicon, aiming at creating an alternative, energy-efficient information technology in which digital data are represented by the orientation of the electron spin. Here we review the cornerstones of silicon spintronics, namely the creation, detection and manipulation of spin polarization in silicon. Ferromagnetic tunnel contacts are the key elements and provide a robust and viable approach to induce and probe spins in silicon, at room temperature. We describe the basic physics of spin tunneling into silicon, the spin-transport devices, the materials aspects and engineering of the magnetic tunnel contacts, and discuss important quantities such as the magnitude of the spin accumulation and the spin lifetime in the silicon. We highlight key experimental achievements and recent progress in the development of a spin-based information technology. (topical review)

  10. SKB - PNC. Development of tunnel radar antennas

    International Nuclear Information System (INIS)

    Falk, L.

    1991-07-01

    Tunnel antennas for the RAMAC borehole radar system have been developed and tested in the field. The antennas are of the loaded dipole type and the receiver and transmitter electronics have been rebuilt to screen them from the antennas. A series of measurements has demonstrated that the radar pulse is short and well shaped and relatively free from ringing, even compared with the existing borehole antennas. Two antenna sets were tested: one centered at 60 MHz and another above 100 MHz. Both produced excellent radar pictures when tested in tunnels in Stripa mine. The antennas have been designed to be easy to carry, since the signal quality often depends on the way the antenna is held relative to electric conductors in the tunnels. (au) (46 figs., 57 refs.)

  11. High Performance Single Nanowire Tunnel Diodes

    DEFF Research Database (Denmark)

    Wallentin, Jesper; Persson, Johan Mikael; Wagner, Jakob Birkedal

    NWs were contacted in a NW-FET setup. Electrical measurements at room temperature display typical tunnel diode behavior, with a Peak-to-Valley Current Ratio (PVCR) as high as 8.2 and a peak current density as high as 329 A/cm2. Low temperature measurements show improved PVCR of up to 27.6....... is the tunnel (Esaki) diode, which provides a low-resistance connection between junctions. We demonstrate an InP-GaAs NW axial heterostructure with tunnel diode behavior. InP and GaAs can be readily n- and p-doped, respectively, and the heterointerface is expected to have an advantageous type II band alignment...

  12. Macroscopic quantum tunneling in a dc SQUID

    International Nuclear Information System (INIS)

    Chen, Y.C.

    1986-01-01

    The theory of macroscopic quantum tunneling is applied to a current-biased dc SQUID whose dynamics can be described by a two-dimensional mechanical system with a dissipative environment. Based on the phenomenological model proposed by Caldeira and Leggett, the dissipative environment is represented by a set of harmonic oscillators coupling to the system. After integrating out the environmental degrees of freedom, an effective Euclidean action is found for the two-dimensional system. The action is used to provide the quantum tunneling rate formalism for the dc SQUID. Under certain conditions, the tunneling rate reduces to that of a single current-biased Josephson junction with an adjustable effective critical current

  13. Production of oscillatory flow in wind tunnels

    Science.gov (United States)

    Al-Asmi, K.; Castro, I. P.

    1993-06-01

    A method for producing oscillatory flow in open-circuit wind tunnels driven by centrifugal fans is described. Performance characteristics of a new device installed on two such tunnels of greatly differing size are presented. It is shown that sinusoidal variations of the working section flow, having peak-to-peak amplitudes up to at least 30 percent of the mean flow speed and frequencies up to, typically, that corresponding to the acoustic quarter-wave-length frequency determined by the tunnel size, can be obtained with negligible harmonic distortion or acoustic noise difficulties. A brief review of the various methods that have been used previously is included, and the advantages and disadvantages of these different techniques are highlighted. The present technique seems to represent a significant improvement over many of them.

  14. Tunnelling through a Gaussian random barrier

    International Nuclear Information System (INIS)

    Bezak, Viktor

    2008-01-01

    A thorough analysis of the tunnelling of electrons through a laterally inhomogeneous rectangular barrier is presented. The barrier height is defined as a statistically homogeneous Gaussian random function. In order to simplify calculations, we assume that the electron energy is low enough in comparison with the mean value of the barrier height. The randomness of the barrier height is defined vertically by a constant variance and horizontally by a finite correlation length. We present detailed calculations of the angular probability density for the tunnelled electrons (i.e. for the scattering forwards). The tunnelling manifests a remarkably diffusive character if the wavelength of the electrons is comparable with the correlation length of the barrier

  15. Phonon tunneling through a double barrier system

    Energy Technology Data Exchange (ETDEWEB)

    Villegas, Diosdado [Departamento de Física, Universidad Central “Marta Abreu” de Las Villas, CP 54830, Santa Clara, Villa Clara (Cuba); Instituto de Física, Universidad Autónoma de Puebla, 18 Sur y San Claudio, Edif. 110A, Ciudad Universitaria, 72570 Puebla (Mexico); León-Pérez, Fernando de [Centro Universitario de la Defensa de Zaragoza, Ctra. de Huesca s/n, E-50090 Zaragoza (Spain); Pérez-Álvarez, R. [Universidad Autónoma del Estado de Morelos, Av. Universidad 1001, CP 62209 Cuernavaca (Mexico); Arriaga, J., E-mail: arriaga@ifuap.buap.mx [Instituto de Física, Universidad Autónoma de Puebla, 18 Sur y San Claudio, Edif. 110A, Ciudad Universitaria, 72570 Puebla (Mexico)

    2015-04-15

    The tunneling of optical and acoustic phonons at normal incidence on a double-barrier is studied in this paper. Transmission coefficients and resonance conditions are derived theoretically under the assumption that the long-wavelength approximation is valid. It is shown that the behavior of the transmission coefficients for the symmetric double barrier has a Lorentzian form close to resonant frequencies and that Breit–Wigner's formula have a general validity in one-dimensional phonon tunneling. Authors also study the so-called generalized Hartman effect in the tunneling of long-wavelength phonons and show that this effect is a numerical artifact resulting from taking the opaque limit before exploring the variation with a finite barrier width. This study could be useful for the design of acoustic devices.

  16. A Top Pilot Tunnel Preconditioning Method for the Prevention of Extremely Intense Rockbursts in Deep Tunnels Excavated by TBMs

    Science.gov (United States)

    Zhang, Chuanqing; Feng, Xiating; Zhou, Hui; Qiu, Shili; Wu, Wenping

    2012-05-01

    The headrace tunnels at the Jinping II Hydropower Station cross the Jinping Mountain with a maximum overburden depth of 2,525 m, where 80% of the strata along the tunnels consist of marble. A number of extremely intense rockbursts occurred during the excavation of the auxiliary tunnels and the drainage tunnel. In particular, a tunnel boring machine (TBM) was destroyed by an extremely intense rockburst in a 7.2-m-diameter drainage tunnel. Two of the four subsequent 12.4-m-diameter headrace tunnels will be excavated with larger size TBMs, where a high risk of extremely intense rockbursts exists. Herein, a top pilot tunnel preconditioning method is proposed to minimize this risk, in which a drilling and blasting method is first recommended for the top pilot tunnel excavation and support, and then the TBM excavation of the main tunnel is conducted. In order to evaluate the mechanical effectiveness of this method, numerical simulation analyses using the failure approaching index, energy release rate, and excess shear stress indices are carried out. Its construction feasibility is discussed as well. Moreover, a microseismic monitoring technique is used in the experimental tunnel section for the real-time monitoring of the microseismic activities of the rock mass in TBM excavation and for assessing the effect of the top pilot tunnel excavation in reducing the risk of rockbursts. This method is applied to two tunnel sections prone to extremely intense rockbursts and leads to a reduction in the risk of rockbursts in TBM excavation.

  17. Coulomb singularity effects in tunnelling spectroscopy of individual impurities

    OpenAIRE

    Arseyev, P. I.; Maslova, N. S.; Panov, V. I.; Savinov, S. V.

    2002-01-01

    Non-equilibrium Coulomb effects in resonant tunnelling processes through deep impurity states are analyzed. It is shown that Coulomb vertex corrections to the tunnelling transfer amplitude lead to a power-law singularity in current- voltage characteristics

  18. 47 CFR 15.211 - Tunnel radio systems.

    Science.gov (United States)

    2010-10-01

    ... regulations contained within this part. (c) The total electromagnetic field from a tunnel radio system on any... surrounding earth and/or water. (b) Any intentional or unintentional radiator external to the tunnel, mine or...

  19. Toward an Integrated Optical Data System for Wind Tunnel Testing

    National Research Council Canada - National Science Library

    Ruyten, Wim

    1999-01-01

    ...) of the test article in a wind tunnel test. The theory for such P&A determinations is developed and applied to data from a recent pressure sensitive paint test in AEDC's 16 ft transonic wind tunnel...

  20. Unified time analysis of photon and particle tunnelling

    International Nuclear Information System (INIS)

    Olkhovsky, V.S.; Recami, Erasmo; Jakiel, Jacek

    2004-01-01

    A unified time analysis of photon and nonrelativistic particle tunnellings is presented, in which time is regarded as a quantum observable, canonically conjugated to energy. Within this approach, one can introduce self-consistent definitions of the tunnelling times, on the basis of conventional quantum mechanics (or one-dimensional quantum electrodynamics) only. The validity of the Hartman effect [which states the tunnelling duration to be independent of the (opaque) barrier width, with superluminal group velocities of the tunnelling packet as a consequence] is verified for all the known expressions of the mean tunnelling time. However, some noticeable generalizations of (and deviations from) the Hartman effect are, as well, briefly investigated. Moreover, the analogy between particle and photon tunnelling is suitably exploited; on the basis of such an analogy, an explanation of some recent interesting microwave and optical experimental results on tunnelling times is proposed. Attention is devoted, at last, to some aspects of the causality problem for particle and photon tunnelling

  1. Problems with tunneling of thin shells from black holes

    Indian Academy of Sciences (India)

    Specifically for shells tunneling out of black holes, this quantity is not invariant under canonical transformations. ... Although such cases include alpha decay, they do not include the tunneling of shells from black holes. ... Current Issue : Vol.

  2. CURRENT ASSET TUNNELING AND FIRM PERFORMANCE IN AN EMERGING MARKET

    Directory of Open Access Journals (Sweden)

    Ratna Candra Sari

    2014-12-01

    Full Text Available This study examines the effect of current asset tunneling on firm performance from the emerging market perspective. Although tunneling activities is a common practices by businesses especially in Indonesia, there exist obstacles in the measurement of tunneling activity because it is difficult to proof the existence of such practices. In this study, we measure tunneling by using accounts receivables and develop tunneling detection criteria. In addition, this study examines the effect of tunneling on firm performance and market reaction during the announcement of the related party transaction. The study finds that from the perspective of the being-tunneled companies, receivables to related parties negatively affect the company’s profit margin. Companies which announce related party transaction indicating tunneling obtain negative abnormal return during the announcement of the related party transaction.

  3. New approach towards imaging -DNA using scanning tunneling

    Indian Academy of Sciences (India)

    DNA; scanning tunneling microscopy; Langmuir Blodget technique; silanization. ... Scanning tunneling spectroscopy (STS) at different stages depict a broad distribution of defect states in the bandgap region of -Si(111) which ... Current Issue

  4. Role of spin polarized tunneling in magnetoresistance and low

    Indian Academy of Sciences (India)

    Role of spin polarized tunneling in magnetoresistance and low temperature minimum of polycrystalline La1–KMnO3 ( = 0.05, 0.1, ... Manganites; magnetoresistance; low temperature resistivity; spin polarized tunneling. ... Current Issue

  5. Robust spin transfer torque in antiferromagnetic tunnel junctions

    KAUST Repository

    Saidaoui, Hamed Ben Mohamed; Waintal, Xavier; Manchon, Aurelien

    2017-01-01

    We theoretically study the current-induced spin torque in antiferromagnetic tunnel junctions, composed of two semi-infinite antiferromagnetic layers separated by a tunnel barrier, in both clean and disordered regimes. We find that the torque

  6. [Occupational carpal tunnel syndrome: 27 cases].

    Science.gov (United States)

    Slimane, Neila Ben; Elleuch, Mohamed; Gharbi, Ezzedine; Babay, Habib; Hamdoun, Moncef

    2010-09-01

    Carpal tunnel syndrome is the most frequent of tunnel syndromes in the field of the professional sphere. It is related to repetitive movements of flexion-extension of the wrist and fingers or to a support on the heel of the hands. To determine the posts in a risk and to specify the modalities of guaranteed reimbursement of professional carpal tunnel syndrome. A retrospective and descriptive study of 27 medical files of employees indemnified for professional carpal tunnel syndrome registered in the medical control services of the social security office in charge of medical insurance of Tunis and Sousse during a period of 10 years (1995-2004). There were 24 women and 3 men with the average age of 40 years all occupying posts in a risk. Their average time of service is 15 years. Tow-thirds of them work in the clothing and textile industry. The attack is bilateral in 13 cases. Nightly acroparaesthesia rules the clinical rate (44.44% of cases). Motor disorders are noted in the quarter of cases. The electromyogram had confirmed diagnosis in all of cases. The previous state study put in evidence the antecedent of carpal tunnel syndrome in 5 cases and diabetes in one case. Twenty-one patients had profit of permanent partial incapacity with a rate varying from 3 to 25%. Five had got a transfer of working place and one stayed in the same post with a half-time work. The professional origin of carpal tunnel syndrome must be called up in front of an activity in a risk. The reparation is done according to picture 82 of occupational diseases.

  7. The Advantages of Lateral Tarsal Strip Procedure

    African Journals Online (AJOL)

    Generally in surgery, an ideal operation should be effective, cause minimal discomfort and morbidity, give an aesthetic result, and have a lasting effect.[4]. Lateral strip procedure (LSP) has those characteristics and it does restore normal lid function and give a rapid rehabilitation with few complications and excellent.

  8. The Advantages of Lateral Tarsal Strip Procedure

    African Journals Online (AJOL)

    E-mail: altieri.ferraris@tin.it. REFERENCES. 1. Olver JM, Barnes JA. Effective small-incision surgery for involutional lower eyelid entropion. Ophthalmology 2000;107:1982-8. 2. Wright M, Bell D, Scott C, Leatherbarrow B. Everting sutures correction of lower lid involutional entropion. Br J Ophthalmol. 1999;83:1060-3.

  9. Generalized Bessel functions in tunnelling ionization

    International Nuclear Information System (INIS)

    Reiss, H R; Krainov, V P

    2003-01-01

    We develop two new approximations for the generalized Bessel function that frequently arises in the analytical treatment of strong-field processes, especially in non-perturbative multiphoton ionization theories. Both these new forms are applicable to the tunnelling environment in atomic ionization, and are analytically much simpler than the currently used low-frequency asymptotic approximation for the generalized Bessel function. The second of the new forms is an approximation to the first, and it is the second new form that exhibits the well-known tunnelling exponential

  10. Application Of Artificial Intelligence To Wind Tunnels

    Science.gov (United States)

    Lo, Ching F.; Steinle, Frank W., Jr.

    1989-01-01

    Report discusses potential use of artificial-intelligence systems to manage wind-tunnel test facilities at Ames Research Center. One of goals of program to obtain experimental data of better quality and otherwise generally increase productivity of facilities. Another goal to increase efficiency and expertise of current personnel and to retain expertise of former personnel. Third goal to increase effectiveness of management through more efficient use of accumulated data. System used to improve schedules of operation and maintenance of tunnels and other equipment, assignment of personnel, distribution of electrical power, and analysis of costs and productivity. Several commercial artificial-intelligence computer programs discussed as possible candidates for use.

  11. Macroscopic quantum tunneling of the magnetic moment

    Science.gov (United States)

    Tejada, J.; Hernandez, J. M.; del Barco, E.

    1999-05-01

    In this paper we review the work done on magnetic relaxation during the last 10 years on both single-domain particles and magnetic molecules and its contribution to the discovery of quantum tunneling of the magnetic moment (Chudnovsky and Tejada, Macroscopic Quantum tunneling of the Magnetic moment, Cambridge University press, Cambridge, 1998). We present first the theoretical expressions and their connection to quantum relaxation and secondly, we show and discuss the experimental results. Finally, we discuss very recent hysteresis data on Mn 12Ac molecules at extremely large sweeping rate for the external magnetic field which suggest the existence of quantum spin—phonon avalanches.

  12. Fire Resistant Panels for the Tunnel Linings

    Directory of Open Access Journals (Sweden)

    Gravit Marina

    2016-01-01

    Full Text Available Presents the results of studies of innovative materials in the field of experimental and theoretical research fire resistance fireproof panels Pyro-Safe Aestuver T. Owing to the assembly simplicity, materials cheapness, high ecological standard, recycling, reuse potential, are benefit. Research work is running to improve the knowledge about fireproof panels Pyro-Safe Aestuver T for tunnel lining, its basic performance, its long term behavior and in particular also its fire proof for example when used for the lining of road tunnels.

  13. Microscopic tunneling theory of long Josephson junctions

    DEFF Research Database (Denmark)

    Grønbech-Jensen, N.; Hattel, Søren A.; Samuelsen, Mogens Rugholm

    1992-01-01

    We present a numerical scheme for solving a nonlinear partial integro-differential equation with nonlocal time dependence. The equation describes the dynamics in a long Josephson junction modeled by use of the microscopic theory for tunneling between superconductors. We demonstrate that the detai......We present a numerical scheme for solving a nonlinear partial integro-differential equation with nonlocal time dependence. The equation describes the dynamics in a long Josephson junction modeled by use of the microscopic theory for tunneling between superconductors. We demonstrate...

  14. Dihydroazulene photoswitch operating in sequential tunneling regime

    DEFF Research Database (Denmark)

    Broman, Søren Lindbæk; Lara-Avila, Samuel; Thisted, Christine Lindbjerg

    2012-01-01

    to electrodes so that the electron transport goes by sequential tunneling. To assure weak coupling, the DHA switching kernel is modified by incorporating p-MeSC6H4 end-groups. Molecules are prepared by Suzuki cross-couplings on suitable halogenated derivatives of DHA. The synthesis presents an expansion of our......, incorporating a p-MeSC6H4 anchoring group in one end, has been placed in a silver nanogap. Conductance measurements justify that transport through both DHA (high resistivity) and VHF (low resistivity) forms goes by sequential tunneling. The switching is fairly reversible and reenterable; after more than 20 ON...

  15. A study for the KAERI research tunnel

    Energy Technology Data Exchange (ETDEWEB)

    Kim, J.; Hwang, Y. S.; Park, H. S.; Park, S. K.; Park, B. Y.; Bang, K. S.; Kuh, J. H.; Kang, K. H

    1997-12-01

    Major goal of the R and D on the KAERI Research Tunnel in 1997 are 1) concept development of the KAERI research tunnel and its major units 2) computer simulation of facilities 3) study on thermo-hydro mechanical coupling in the vicinity of a waste repository 4) effect of excavated distrubed zone. In addition supplementary site investigation to understand the distribution of stresses in the site was done along with long term monitoring of the water table. (author). 44 refs., 16 tabs., 36 figs

  16. Spectral tunneling of lattice nonlocal solitons

    International Nuclear Information System (INIS)

    Kartashov, Yaroslav V.; Torner, Lluis; Vysloukh, Victor A.

    2010-01-01

    We address spectral tunneling of walking spatial solitons in photorefractive media with nonlocal diffusion component of the nonlinear response and an imprinted shallow optical lattice. In contrast to materials with local nonlinearities, where solitons traveling across the lattice close to the Bragg angle suffer large radiative losses, in photorefractive media with diffusion nonlinearity resulting in self-bending, solitons survive when their propagation angle approaches and even exceeds the Bragg angle. In the spatial frequency domain this effect can be considered as tunneling through the band of spatial frequencies centered around the Bragg frequency where the spatial group velocity dispersion is positive.

  17. Wind Tunnel Measurements at LM Wind Power

    DEFF Research Database (Denmark)

    Bertagnolio, Franck

    2012-01-01

    This section presents the results obtained during the experimental campaign that was conducted in the wind tunnel at LM Wind Power in Lunderskov from August 16th to 26th, 2010. The goal of this study is to validate the so-called TNO trailing edge noise model through measurements of the boundary...... layer turbulence characteristics and the far-field noise generated by the acoustic scattering of the turbulent boundary layer vorticies as they convect past the trailing edge. This campaign was conducted with a NACA0015 airfoil section that was placed in the wind tunnel section. It is equipped with high...

  18. Microwave-induced co-tunneling in single electron tunneling transistors

    DEFF Research Database (Denmark)

    Ejrnaes, M.; Savolainen, M.; Manscher, M.

    2002-01-01

    on rubber bellows. Cross-talk was minimized by using individual coaxial lines between the sample and the room temperature electronics: The co-tunneling experiments were performed at zero DC bias current by measuring the voltage response to a very small amplitude 2 Hz current modulation with the gate voltage......The influence of microwaves on the co-tunneling in single electron tunneling transistors has been investigated as function of frequency and power in the temperature range from 150 to 500 mK. All 20 low frequency connections and the RF line were filtered, and the whole cryostat was suspended...

  19. Fabrication of magnetic tunnel junctions with epitaxial and textured ferromagnetic layers

    Science.gov (United States)

    Chang, Y. Austin; Yang, Jianhua Joshua

    2008-11-11

    This invention relates to magnetic tunnel junctions and methods for making the magnetic tunnel junctions. The magnetic tunnel junctions include a tunnel barrier oxide layer sandwiched between two ferromagnetic layers both of which are epitaxial or textured with respect to the underlying substrate upon which the magnetic tunnel junctions are grown. The magnetic tunnel junctions provide improved magnetic properties, sharper interfaces and few defects.

  20. Acute abdomen

    Directory of Open Access Journals (Sweden)

    Wig J

    1978-01-01

    Full Text Available 550 cases of acute abdomen have been analysed in detail includ-ing their clinical presentation and operative findings. Males are more frequently affected than females in a ratio of 3: 1. More than 45% of patients presented after 48 hours of onset of symptoms. Intestinal obstruction was the commonest cause of acute abdomen (47.6%. External hernia was responsible for 26% of cases of intestinal obstruction. Perforated peptic ulcer was the commonest cause of peritonitis in the present series (31.7% while incidence of biliary peritonitis was only 2.4%.. The clinical accuracy rate was 87%. The mortality in operated cases was high (10% while the over-all mortality rate was 7.5%.

  1. Acute Blindness.

    Science.gov (United States)

    Meekins, Jessica M

    2015-09-01

    Sudden loss of vision is an ophthalmic emergency with numerous possible causes. Abnormalities may occur at any point within the complex vision pathway, from retina to optic nerve to the visual center in the occipital lobe. This article reviews specific prechiasm (retina and optic nerve) and cerebral cortical diseases that lead to acute blindness. Information regarding specific etiologies, pathophysiology, diagnosis, treatment, and prognosis for vision is discussed. Copyright © 2015 Elsevier Inc. All rights reserved.

  2. Tunnel operator training with a conversational agent-assistant

    NARCIS (Netherlands)

    Buiel, E.; Lubbers, J.; Doesburg, W. van; Muller, T.

    2009-01-01

    A tunnel operator monitors and regulates the flow of traffic inside a tunnel. Tunnel operators need to train in a simulator regularly in order to maintain proficiency in handling incident situations. During quiet working hours, the operator has enough time for training. But generally at that time no

  3. Tunneling and propping : a justification for pyramidal ownership

    NARCIS (Netherlands)

    Riyanto, Y.E.; Toolsema-Veldman, Linda

    2004-01-01

    This paper presents a formal model of tunneling and propping in a pyramidal ownership structure. Tunneling refers to controlling shareholders shifting resources from one firm to another in the same pyramid. Propping is tunneling that is done to save the receiving firm from bankruptcy. We compare the

  4. Spin polarization at the interface and tunnel magnetoresistance

    International Nuclear Information System (INIS)

    Itoh, H.; Inoue, J.

    2001-01-01

    We propose that interfacial states of imperfectly oxidized Al ions may exist in ferromagnetic tunnel junctions with Al-O barrier and govern both the spin polarization and tunnel conductance. It is shown that the spin polarization is positive independent of materials and correlates well with the tunnel magnetoresistance

  5. Modeling of inter-ribbon tunneling in graphene

    OpenAIRE

    Van de Put, Maarten L.; Vandenberghe, William G.; Sorée, Bart; Magnus, Wim; Fischetti, Massimo

    2015-01-01

    The tunneling current between two crossed graphene ribbons is described invoking the empirical pseudopotential approximation and the Bardeen transfer Hamiltonian method. Results indicate that the density of states is the most important factor determining the tunneling current between small (nm) ribbons. The quasi-one dimensional nature of graphene nanoribbons is shown to result in resonant tunneling.

  6. Asymmetric voltage behavior of the tunnel magnetoresistance in double barrier magnetic tunnel junctions

    KAUST Repository

    Useinov, Arthur

    2012-06-01

    In this paper, we study the value of the tunnel magnetoresistance (TMR) as a function of the applied voltage in double barrier magnetic tunnel junctions (DMTJs) with the left and right ferromagnetic (FM) layers being pinned and numerically estimate the possible difference of the TMR curves for negative and positive voltages in the homojunctions (equal barriers and electrodes). DMTJs are modeled as two single barrier junctions connected in series with consecutive tunneling (CST). We investigated the asymmetric voltage behavior of the TMR for the CST in the range of a general theoretical model. Significant asymmetries of the experimental curves, which arise due to different annealing regimes, are mostly explained by different heights of the tunnel barriers and asymmetries of spin polarizations in magnetic layers. © (2012) Trans Tech Publications.

  7. Anomalous Tunnel Magnetoresistance and Spin Transfer Torque in Magnetic Tunnel Junctions with Embedded Nanoparticles

    Science.gov (United States)

    Useinov, Arthur; Ye, Lin-Xiu; Useinov, Niazbeck; Wu, Te-Ho; Lai, Chih-Huang

    2015-01-01

    The tunnel magnetoresistance (TMR) in the magnetic tunnel junction (MTJ) with embedded nanoparticles (NPs) was calculated in range of the quantum-ballistic model. The simulation was performed for electron tunneling through the insulating layer with embedded magnetic and non-magnetic NPs within the approach of the double barrier subsystem connected in parallel to the single barrier one. This model can be applied for both MTJs with in-plane magnetization and perpendicular one. We also calculated the in-plane component of the spin transfer torque (STT) versus the applied voltage in MTJs with magnetic NPs and determined that its value can be much larger than in single barrier system (SBS) for the same tunneling thickness. The reported simulation reproduces experimental data of the TMR suppression and peak-like TMR anomalies at low voltages available in leterature. PMID:26681336

  8. Theoretical consideration of spin-polarized resonant tunneling in magnetic tunnel junctions

    International Nuclear Information System (INIS)

    Mu Haifeng; Zhu Zhengang; Zheng Qingrong; Jin Biao; Wang Zhengchuan; Su Gang

    2004-01-01

    A recent elegant experimental realization [S. Yuasa et al., Science 297 (2002) 234] of the spin-polarized resonant tunneling in magnetic tunnel junctions is interpreted in terms of a two-band model. It is shown that the tunnel magnetoresistance (TMR) decays oscillatorily with the thickness of the normal metal (NM) layer, being fairly in agreement with the experimental observation. The tunnel conductance is found to decay with slight oscillations with the increase of the NM layer thickness, which is also well consistent with the experiment. In addition, when the magnetizations of both ferromagnet electrodes are not collinearly aligned, TMR is found to exhibit sharp resonant peaks at some particular thickness of the NM layer. The peaked TMR obeys nicely a Gaussian distribution against the relative orientation of the magnetizations

  9. Resonant tunnel magnetoresistance in double-barrier planar magnetic tunnel junctions

    KAUST Repository

    Useinov, A. N.

    2011-08-24

    We present a theoretical approach to calculate the spin-dependent current and tunnel magnetoresistance (TMR) in a double-barrier magnetic tunnel junction (DMTJ), in which the magnetization of the middle ferromagnetic metal layer can be aligned parallel or antiparallel in relation to the fixed magnetizations of the left and right ferromagnetic electrodes. The electron transport through the DMTJ is considered as a three-dimensional problem, taking into account all transmitting electron trajectories as well as the spin-dependent momentum conservation law. The dependence of the transmission coefficient and spin-polarized currents on the applied voltage is derived as an exact solution to the quantum-mechanical problem for the spin-polarized transport. In the range of the developed physical model, the resonant tunneling, nonresonant tunneling, and enhanced spin filtering can be explained; the simulation results are in good agreement with experimental data.

  10. Resonant tunnel magnetoresistance in double-barrier planar magnetic tunnel junctions

    KAUST Repository

    Useinov, A. N.; Kosel, Jü rgen; Useinov, N. Kh.; Tagirov, L. R.

    2011-01-01

    We present a theoretical approach to calculate the spin-dependent current and tunnel magnetoresistance (TMR) in a double-barrier magnetic tunnel junction (DMTJ), in which the magnetization of the middle ferromagnetic metal layer can be aligned parallel or antiparallel in relation to the fixed magnetizations of the left and right ferromagnetic electrodes. The electron transport through the DMTJ is considered as a three-dimensional problem, taking into account all transmitting electron trajectories as well as the spin-dependent momentum conservation law. The dependence of the transmission coefficient and spin-polarized currents on the applied voltage is derived as an exact solution to the quantum-mechanical problem for the spin-polarized transport. In the range of the developed physical model, the resonant tunneling, nonresonant tunneling, and enhanced spin filtering can be explained; the simulation results are in good agreement with experimental data.

  11. Electrically tunable tunneling rectification magnetoresistance in magnetic tunneling junctions with asymmetric barriers.

    Science.gov (United States)

    Wang, Jing; Huang, Qikun; Shi, Peng; Zhang, Kun; Tian, Yufeng; Yan, Shishen; Chen, Yanxue; Liu, Guolei; Kang, Shishou; Mei, Liangmo

    2017-10-26

    The development of multifunctional spintronic devices requires simultaneous control of multiple degrees of freedom of electrons, such as charge, spin and orbit, and especially a new physical functionality can be realized by combining two or more different physical mechanisms in one specific device. Here, we report the realization of novel tunneling rectification magnetoresistance (TRMR), where the charge-related rectification and spin-dependent tunneling magnetoresistance are integrated in Co/CoO-ZnO/Co magnetic tunneling junctions with asymmetric tunneling barriers. Moreover, by simultaneously applying direct current and alternating current to the devices, the TRMR has been remarkably tuned in the range from -300% to 2200% at low temperature. This proof-of-concept investigation provides an unexplored avenue towards electrical and magnetic control of charge and spin, which may apply to other heterojunctions to give rise to more fascinating emergent functionalities for future spintronics applications.

  12. Asymmetric voltage behavior of the tunnel magnetoresistance in double barrier magnetic tunnel junctions

    KAUST Repository

    Useinov, Arthur; Gooneratne, Chinthaka Pasan; Kosel, Jü rgen

    2012-01-01

    In this paper, we study the value of the tunnel magnetoresistance (TMR) as a function of the applied voltage in double barrier magnetic tunnel junctions (DMTJs) with the left and right ferromagnetic (FM) layers being pinned and numerically estimate the possible difference of the TMR curves for negative and positive voltages in the homojunctions (equal barriers and electrodes). DMTJs are modeled as two single barrier junctions connected in series with consecutive tunneling (CST). We investigated the asymmetric voltage behavior of the TMR for the CST in the range of a general theoretical model. Significant asymmetries of the experimental curves, which arise due to different annealing regimes, are mostly explained by different heights of the tunnel barriers and asymmetries of spin polarizations in magnetic layers. © (2012) Trans Tech Publications.

  13. Study of tunneling transport in Si-based tunnel field-effect transistors with ON current enhancement utilizing isoelectronic trap

    Science.gov (United States)

    Mori, Takahiro; Morita, Yukinori; Miyata, Noriyuki; Migita, Shinji; Fukuda, Koichi; Mizubayashi, Wataru; Masahara, Meishoku; Yasuda, Tetsuji; Ota, Hiroyuki

    2015-02-01

    The temperature dependence of the tunneling transport characteristics of Si diodes with an isoelectronic impurity has been investigated in order to clarify the mechanism of the ON-current enhancement in Si-based tunnel field-effect transistors (TFETs) utilizing an isoelectronic trap (IET). The Al-N complex impurity was utilized for IET formation. We observed three types of tunneling current components in the diodes: indirect band-to-band tunneling (BTBT), trap-assisted tunneling (TAT), and thermally inactive tunneling. The indirect BTBT and TAT current components can be distinguished with the plot described in this paper. The thermally inactive tunneling current probably originated from tunneling consisting of two paths: tunneling between the valence band and the IET trap and tunneling between the IET trap and the conduction band. The probability of thermally inactive tunneling with the Al-N IET state is higher than the others. Utilization of the thermally inactive tunneling current has a significant effect in enhancing the driving current of Si-based TFETs.

  14. Tunneling times and the Hartman effect revisited

    Energy Technology Data Exchange (ETDEWEB)

    Olkhovsky, Vladislav S. [Ukrainian Academy of Sciences, Kiev (Ukraine). Inst. for Nuclear Research]|[Istituto Nazionale di Fisica Nucleare, Catania (Italy); Recami, Erasmo [Universidade Estadual de Campinas, SP (Brazil). Dept. de Matematica Aplicada]|[Istituto Nazionale di Fisica Nucleare, Milano (Italy); Raciti, Fabio [Catania Univ. (Italy). Dipt. di Fisica; Zaichenko, Aleksandr K. [Ukrainian Academy of Sciences, Kiev (Ukraine)

    1995-05-01

    In a recent review paper we proposed, within conventional quantum mechanics, new definitions for the sub-barrier tunnelling and reflection times. Aims of the present paper are: presenting and analysing the results of various numerical calculations (based on our equations) on the penetration and return times < {tau}Pen >, <{tau}Ret >, during tunneling inside a rectangular potential barrier, for various penetration depths x{sub f}; putting forth and discussing suitable definitions, besides of the mean values, also of the variances (or dispersions) D {sup {tau}}T D {sup {tau}}R for the time durations of transmission and reflection process; mentioning that our definition < {sup {tau}}T > for the average transmission time results to constitute an improvement of the ordinary dwell-time {tau}{sup Dw} formula; commenting upon some recent criticism by C.R. Leavens, on the basis of our new numerical results. We stress that our numerical evaluations confirm that our approach implied and implies, the existence of the Hartman effect: an effect that in these days (due to the theoretical connections between tunneling and evanescent wave propagation) is receiving - at Cologne, Berkeley, Florence and Vienna- indirect, but quite interesting, experimental verifications. At last, we briefly analyze some other definitions of tunnelling times. (author). 24 refs., 5 figs.

  15. Enhanced Tunnelling Models for Child Universe Formation

    CERN Document Server

    Ansoldi, S; Shilon, I

    2015-01-01

    Starting from a recently proposed model that allows for an enhanced rate of child universe production under generic conditions, we elaborate on refinements that may allow for non-singular initial configurations. A possibility to treat both, the initial state and the tunnelling beyond the semiclassical level will also be introduced.

  16. Tents and tunnels on martensitic films

    International Nuclear Information System (INIS)

    Bhattacharya, K.; Hane, K.F.; James, R.D.; Palmstroem, C.J.

    1999-01-01

    In this paper we outline a strategy for producing certain deformable structures - tents and tunnels - on epitaxially grown martensitic single crystal films. These structures are intended to be the basic building blocks of micropumps and microactuators. We give specific predictions for the systems Ni 2 MnGa, PbTiO 3 and Cu-Zn-Al. (orig.)

  17. A Student-Built Scanning Tunneling Microscope

    Science.gov (United States)

    Ekkens, Tom

    2015-01-01

    Many introductory and nanotechnology textbooks discuss the operation of various microscopes including atomic force (AFM), scanning tunneling (STM), and scanning electron microscopes (SEM). In a nanotechnology laboratory class, students frequently utilize microscopes to obtain data without a thought about the detailed operation of the tool itself.…

  18. New directions in scanning-tunneling microscopy

    International Nuclear Information System (INIS)

    Ferrell, T.L.; Warmack, R.J.; Reddick, R.C.

    1989-01-01

    The tunneling of electrons in scanning-tunneling microscopy (STM) has permitted imaging of the electronic distribution about individual atoms on surfaces. The need for use of conducting surfaces in STM limits its applicability, and new forms of scanning microscopy have emerged as a result of interest in poorly conducting samples. Atomic force microscopy has demonstrated that the force between a surface and a probe tip can be used to image selected materials. Now being developed are magnetic probe STM's and photon tunneling microscopes in which the probe is a sharpened optical fiber. Also of great interest presently is the measurement of differential conductance of surfaces using electron STM's. This method supplies spectral information and contrast enhancement in images. At present there remains much theoretical work to be carried out in order to better characterize related data on inelastic electron tunneling, and valuable insight may be gained from data being gathered on the local work function of materials. As matters stand today, the key problems lie in determining tip and contamination effects, preparation of samples, and understanding conductivity mechanisms in very thin materials on conducting substrates. Resolution of these problems and introduction of new forms of scanning microscopy may permit novel and important applications in biology as well as surface science

  19. Study of Scanning Tunneling Microscope control electronics

    International Nuclear Information System (INIS)

    Oliva, A.J.; Pancarobo, M.; Denisenko, N.; Aguilar, M.; Rejon, V.; Pena, J.L.

    1994-01-01

    A theoretical study of Scanning Tunneling Microscope control electronics is made. The knowledge of its behaviour allows us to determine accurately the region where the unstable operation could effect the measurements, and also to set the optimal working parameters. Each feedback circuitry compound is discussed as well as their mutual interaction. Different working conditions analysis and results are presented. (Author) 12 refs

  20. 75 FR 42643 - National Tunnel Inspection Standards

    Science.gov (United States)

    2010-07-22

    ... individual submitting the comment (or signing the comment, if submitted on behalf of an association, business... (such as faults, aggressive or corrosive soils), tunnel location importance, strategic values, seismic... that there should be a distinction between qualification requirements for Team Leaders and for other...

  1. Tunneling times and the Hartman effect revisited

    International Nuclear Information System (INIS)

    Olkhovsky, Vladislav S.; Recami, Erasmo; Raciti, Fabio

    1995-05-01

    In a recent review paper we proposed, within conventional quantum mechanics, new definitions for the sub-barrier tunnelling and reflection times. Aims of the present paper are: presenting and analysing the results of various numerical calculations (based on our equations) on the penetration and return times , , during tunneling inside a rectangular potential barrier, for various penetration depths x f ; putting forth and discussing suitable definitions, besides of the mean values, also of the variances (or dispersions) D τ T D τ R for the time durations of transmission and reflection process; mentioning that our definition τ T > for the average transmission time results to constitute an improvement of the ordinary dwell-time τ Dw formula; commenting upon some recent criticism by C.R. Leavens, on the basis of our new numerical results. We stress that our numerical evaluations confirm that our approach implied and implies, the existence of the Hartman effect: an effect that in these days (due to the theoretical connections between tunneling and evanescent wave propagation) is receiving - at Cologne, Berkeley, Florence and Vienna- indirect, but quite interesting, experimental verifications. At last, we briefly analyze some other definitions of tunnelling times. (author). 24 refs., 5 figs

  2. Backfilling of deposition tunnels, block alternative

    International Nuclear Information System (INIS)

    Keto, P.; Roennqvist, P.-E.

    2007-03-01

    This report presents a preliminary process description of backfilling the deposition tunnels with pre-compacted blocks consisting of a mixture of bentonite and ballast (30:70). The process was modified for the Finnish KBS-3V type repository assuming that the amount of spent fuel canisters disposed of yearly is 40. Backfilling blocks (400 x 300 x 300 mm) are prepared in a block production plant with a hydraulic press with an estimated production capacity of 840 blocks per day. Some of the blocks are modified further to fit the profile of the tunnel roof. Prior to the installation of the blocks, the deposition tunnel floor is levelled with a mixture of bentonite and ballast (15:85). The blocks are placed in the tunnel with a modified reach truck. Centrifugal pellet throwing equipment is used to fill the gap between the blocks and the rock surface with bentonite pellets. Based on a preliminary assessment, the average dry density achieved with block backfill is sufficient to fulfil the criteria set for the backfill in order to ensure long-term safety and radiation protection. However, there are uncertainties concerning saturation, homogenisation, erosion, piping and self-healing of the block backfill that need to be studied further with laboratory and field tests. In addition, development efforts and testing concerning block manufacturing and installation are required to verify the technical feasibility of the concept. (orig.)

  3. Electron accelerator for tunneling through hard rock

    International Nuclear Information System (INIS)

    Avery, R.T.; Keefe, D.

    1975-10-01

    Earlier work demonstrated that intense sub-microsecond bursts of energetic electrons cause significant pulverization and spalling of a variety of rock types. The spall debris generally consists of sand, dust, and small flakes. If carried out at rapid repetition rate, this can lead to a promising technique for increasing the speed and reducing the cost of underground excavation of tunnels, mines, and storage spaces. The conceptual design features of a Pulsed Electron Tunnel Excavator capable of tunneling approximately ten times faster than conventional drill/blast methods are presented, with primary emphasis on the electron accelerator and only a brief description of the tunneling aspects. Of several candidate types of accelerators, a linear induction accelerator producing electron pulses (5 MV, 5 kA, 1.0 μs = 25 kJ) at a 360 Hz rate was selected for the conceptual example. This provides the required average electron beam power output of 9 MW. The feasibility of such an accelerator is discussed

  4. Electron accelerator for tunneling through hard rock

    International Nuclear Information System (INIS)

    Avery, R.T.; Keefe, D.

    1975-01-01

    Earlier work demonstrated that intense sub-microsecond bursts of energetic electrons cause significant pulverization and spalling of a variety of rock types. The spall debris generally consists of sand, dust, and small flakes. If carried out at rapid repetition rate, this can lead to a promising technique for increasing the speed and reducing the cost of underground excavation of tunnels, mines, and storage spaces. The conceptual design features of a Pulsed Electron Tunnel Excavator capable of tunneling approximately ten times faster than conventional drill/blast methods are presented with primary emphasis on the electron accelerator and only a brief description of the tunneling aspects. Of several candidate types of accelerators, a linear induction accelerator producing electron pulses (5 MV, 5 kA, 1.0 μs = 25 kJ) at a 360 Hz rate was selected for the conceptual example. This provides the required average electron beam power output of 9 MW. The feasibility of such an accelerator is discussed

  5. Low temperature delayed recombinationand trap tunneling

    Czech Academy of Sciences Publication Activity Database

    Mihóková, Eva; Schulman, L. S.

    2015-01-01

    Roč. 27, č. 7 (2015), 1-8 ISSN 0953-8984 Grant - others:AVČR(CZ) M100101212 Institutional support: RVO:68378271 Keywords : scintillator * tunneling * traps Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 2.209, year: 2015

  6. The overshoot problem in inflation after tunneling

    Energy Technology Data Exchange (ETDEWEB)

    Dutta, Koushik; Vaudrevange, Pascal M.; Westphal, Alexander

    2011-09-15

    We show the absence of the usual parametrically large overshoot problem of small-field inflation if initiated by a Coleman-De Luccia (CDL) tunneling transition from an earlier vacuum in the limit of small inflationary scale compared to the tunneling scale. For low-power monomial exit potentials V({phi}){proportional_to} {phi}{sup n}; n<4, we derive an expression for the amount of overshoot. This is bounded from above by the width of the steep barrier traversed after emerging from tunneling and before reaching a slow-roll region of the potential. For n{>=}4 we show that overshooting is entirely absent. We extend this result through binomials to a general potential written as a series expansion, and to the case of arbitrary finite initial speed of the inflaton. This places the phase space of initial conditions for small-field and large-field inflation on the same footing in a landscape of string theory vacua populated via CDL tunneling. (orig.)

  7. Engineered quantum tunnelling in extended periodic potentials

    Energy Technology Data Exchange (ETDEWEB)

    Wimberger, Sandro; Ciampini, Donatella; Morsch, Oliver; Mannella, Riccardo; Arimondo, Ennio [CNR-INFM and Dipartimento di Fisica ' Enrico Fermi' , Largo Pontecorvo 3, 1-56127 Pisa (Italy)

    2007-05-15

    Quantum tunnelling from a tilted, but otherwise periodic potential is studied. Our theoretical and experimental results show that, by controlling the system's parameters, we can engineer the escape rate of a Bose-Einstein condensate to an exceptional degree. Possible applications of this atom-optics realization of the open Wannier-Stark system are discussed.

  8. Tunnel Diode Discriminator with Fixed Dead Time

    DEFF Research Database (Denmark)

    Diamond, J. M.

    1965-01-01

    A solid state discriminator for the range 0.4 to 10 V is described. Tunnel diodes are used for the discriminator element and in a special fixed dead time circuit. An analysis of temperature stability is presented. The regulated power supplies are described, including a special negative resistance...

  9. Resonant tunneling in a pulsed phonon field

    DEFF Research Database (Denmark)

    Kral, P.; Jauho, Antti-Pekka

    1999-01-01

    , The nonequilibrium spectral function for the resonance displays the formation and decay of the phonon sidebands on ultrashort time scales. The time-dependent tunneling current through the individual phonon satellites reflects this quasiparticle formation by oscillations, whose time scale is set by the frequency...

  10. Tunneling in cuprate and bismuthate superconductors

    International Nuclear Information System (INIS)

    Zasadzinski, J.F.; Huang, Qiang; Tralshawala, N.

    1991-10-01

    Tunneling measurements using a point-contact technique are reported for the following high temperature superconducting oxides: Ba 1-x K x BiO 3 (BKBO), Nd 2-x Ce x CuO 4 (NCCO), Bi 2 Sr 2 CaCu 2 O 7 (BSCCO) and Tl 2 Ba 2 CaCu 2 O x (TBCCO). For the bismuthate, BKBO, ideal, S-I-N tunneling characteristics are observed using a Au tip. The normalized conductance is fitted to a BCS density of states and thermal smearing only proving there is no fundamental limitation in BKBO for device applications. For the cuprates, the normalized conductance displays BCS-like characteristics, but with a broadening larger than from thermal smearing. Energy gap values are presented for each material. For BKBO and NCCO the Eliashberg functions, α 2 F(ω), obtained from the tunneling are shown to be in good agreement with neutron scattering results. Proximity effect tunneling studies are reported for Au/BSCCO bilayers and show that the energy gap of BSCCO can be observed through Au layers up to 600 Angstrom thick

  11. Spin Tunneling in Junctions with Disordered Ferromagnets

    NARCIS (Netherlands)

    Paluskar, P.V.; Attema, J.J.; de Wijs, G.A.; Fiddy, S.; Snoeck, E.; Kohlhepp, J.T.; Swagten, H.J.M.; de Groot, R. A.; Koopmans, H.

    2008-01-01

    We provide compelling evidence to establish that, contrary to one’s elementary guess, the tunneling spin polarization (TSP) of amorphous CoFeB is larger than that of fcc CoFeB. First-principles atomic and electronic structure calculations reveal striking agreement between the measured TSP and the

  12. ENGINEERING GEOLOGY PROPERTIES OF 'KONJSKO' TUNNEL

    Directory of Open Access Journals (Sweden)

    Ivan Grabovac

    2004-12-01

    Full Text Available Investigation works for the design of the Konjsko Tunnel with two pipes, part of the Split-Zagreb Motorway, provided relevant data on rock mass and soil properties for construction of the prognose engineering-geological longitudinal sections. West tunnel portals are situated in tectonically deformed and partly dynamically metamorphosed Eocene flysch marls, while east ones are located in Senonian limestones. There is an overthrust contact between flysch marls and limestones. With the beginning of the excavations, rock mass characteristics were regularly registered after each blasting and actual longitudinal engineering-geological cross-sections were constructed as well as cross-sections of the excavation face. There were some differences between prognosticated and registered sections since it was infeasible to accurately determine the dip of the overthrust plane that was at shallow depth below the tunnel grade line and also due to the occurrence of transversal faults that intersected the overthrust. Data collected before and during the tunnel construction complemented the knowledge on geological structure of the surroundings and physical-mechanical characteristics of strata (the paper is published in Croatian.

  13. Decompression of magma into repository tunnels

    NARCIS (Netherlands)

    Bokhove, Onno; Woods, A.W.

    2002-01-01

    It is nontrivial to find and design safe repository sites for nuclear waste. It appears common sense to drill tunnels as repository sites in a mountain in remote and relatively dry regions. However, erosion of the waste canisters by naturally abundant chemicals in the mountains water cycle remains a

  14. Wind Tunnel Measurements at Virginia Tech

    DEFF Research Database (Denmark)

    Fischer, Andreas; Bertagnolio, Franck

    2012-01-01

    In this section, the wind tunnel configuration used for aerodynamic and aeroacoustic measurement is described. Then, the validation of the method for evaluating far-field noise from surface microphones as described in Section 5 is presented. Finally, the design concept proposed in Section 6 is ve...

  15. Dark matter searches at the Canfranc tunnel

    International Nuclear Information System (INIS)

    Sarsa, M.L.; Avignone, F.T.; Brodzinski, R.L.; Cerezo, E.; Collar, J.I.; Garcia, E.; Reeves, J.H.; Miley, H.S.; Morales, A.; Morales, J.; Nunez-Lagos, R.; Ortiz de Solorzano, A.; Puimedon, J.; Saenz, C.; Salinas, A.; Villar, J.A.

    1994-01-01

    Results of an on-going search for particle dark matter with a germanium detector at the Canfranc tunnel are reported. Contour limits for cross-sections, masses and local halo densities of particles interacting through spin-independent interactions are presented. Preliminary results and prospects of a search for timing modulation of the signal are also reported. ((orig.))

  16. The Femarnbelt Tunnel: Regional Development Perspectives

    DEFF Research Database (Denmark)

    Matthiessen, Christian Wichmann; Lundhus, Peter

    2011-01-01

    structures (bridges/ tunnels) spanning international waterways. They concentrate traffic flows and create strong transport corridors and are the basis of new regional development regimes. In early 2011, following almost two years of extensive work on different conceptual designs for the fixed link...

  17. High-Performance Single Nanowire Tunnel Diodes

    DEFF Research Database (Denmark)

    Wallentin, Jesper; Persson, Johan Mikael; Wagner, Jakob Birkedal

    2010-01-01

    We demonstrate single nanowire tunnel diodes with room temperature peak current densities of up to 329 A/cm(2). Despite the large surface to volume ratio of the type-II InP-GaAs axial heterostructure nanowires, we measure peak to valley current ratios (PVCR) of up to 8.2 at room temperature and 27...

  18. Josephson tunneling in bilayer quantum Hall system

    International Nuclear Information System (INIS)

    Ezawa, Z.F.; Tsitsishvili, G.; Sawada, A.

    2012-01-01

    A Bose–Einstein condensation is formed by composite bosons in the quantum Hall state. A composite boson carries the fundamental charge (−e). We investigate Josephson tunneling of such charges in the bilayer quantum Hall system at the total filling ν=1. We show the existence of the critical current for the tunneling current to be coherent and dissipationless. Our results explain recent experiments due to [L. Tiemann, Y. Yoon, W. Dietsche, K. von Klitzing, W. Wegscheider, Phys. Rev. B 80 (2009) 165120] and due to [Y. Yoon, L. Tiemann, S. Schmult, W. Dietsche, K. von Klitzing, Phys. Rev. Lett. 104 (2010) 116802]. We predict also how the critical current changes as the sample is tilted in the magnetic field. -- Highlights: ► Composite bosons undergo Bose–Einstein condensation to form the bilayer quantum Hall state. ► A composite boson is a single electron bound to a flux quantum and carries one unit charge. ► Quantum coherence develops due to the condensation. ► Quantum coherence drives the supercurrent in each layer and the tunneling current. ► There exists the critical input current so that the tunneling current is coherent and dissipationless.

  19. Dynamic response of tunnels in jointed rocks

    International Nuclear Information System (INIS)

    Heuze, F.E.; Shaffer, R.J.; Walton, O.R.; Maddix, D.M.

    1992-03-01

    We describe the application of the Discrete Element Method (DEM) to the dynamic analysis of the response of tunnels in jointed rocks to earthquake loading. In situations where large motions of many blocks and collapse occur, the discontinuum-based DEM approach appears superior to other methods of analysis

  20. Carrier tunneling in high magnetic fields

    NARCIS (Netherlands)

    Christianen, P.C.M.; Bruggink, I.E.M.; Maan, J.C.; Vleuten, van der W.C.

    1995-01-01

    Proceedings of the XXIV International School of Semiconducting Coinpounds, Jaszowiec 1995. A magnetic field induced coupling is observed between the Landau levels with different quantum number of two GaAs quantum wells separated by a thin (Ga,Al)As tunnel barrier using

  1. Tunneling rates in electron transport through double-barrier molecular junctions in a scanning tunneling microscope

    OpenAIRE

    Nazin, G. V.; Wu, S. W.; Ho, W.

    2005-01-01

    The scanning tunneling microscope enables atomic-scale measurements of electron transport through individual molecules. Copper phthalocyanine and magnesium porphine molecules adsorbed on a thin oxide film grown on the NiAl(110) surface were probed. The single-molecule junctions contained two tunneling barriers, vacuum gap, and oxide film. Differential conductance spectroscopy shows that electron transport occurs via vibronic states of the molecules. The intensity of spectral peaks correspondi...

  2. Derivation of the tunnelling exchange time for the model of trap-assisted tunnelling

    International Nuclear Information System (INIS)

    Racko, J.; Ballo, P.; Benko, P.; Harmatha, L.; Grmanova, A.; Breza, J.

    2014-01-01

    We present derivation of the tunnelling exchange times that play the key role in the model of trap assisted tunnelling (TAT) considering the electron and hole exchange processes between the trapping centre lying in the forbidden band of the semiconductor and the conduction band, valence band or a metal. All exchange processes are quantitatively described by respective exchange times. The reciprocal values of these exchange times represent the frequency with which the exchange processes contribute to the probability of occupation of the trap by free charge carriers. The crucial problem in any model of TAT is the calculation of the occupation probability. In our approach this probability is expressed in terms of only thermal and tunnelling exchange times. The concept of tunnelling exchange times presents a dominant contribution to our model of TAT. The new approach allows to simply calculate the probability of occupation of the trapping centre by a free charge carrier and subsequently to get the thermal and tunnelling generation-recombination rates occurring in the continuity equations. This is why the TAT model based on thermal and tunnelling exchange times is suitable for simulating the electrical properties of semiconductor nanostructures in which quantum mechanical phenomena play a key role. (authors)

  3. Optimization of a tunneling barrier in magnetic tunneling junction by tilted-plasma oxidation

    International Nuclear Information System (INIS)

    Nam, C.H.; Shim, Heejae; Kim, K.S.; Cho, B.K.

    2004-01-01

    Oxidation of an AlO x insulating barrier in a magnetic tunneling junction (MTJ) was carried out by a tilted-plasma oxidation method. It was found that the tilted-plasma oxidation induced a gradual change in the extent of oxidation of an insulating layer, which consequently led to a gradual change in the tunneling magnetoresistance (TMR) and specific junction resistance (RA) of the MTJ. We found a linear relation in the TMR versus RA curve with positive and negative slopes for less- and overoxidized junctions, respectively, and a parabolic relation for optimally oxidized junctions. The crossover in the TMR versus RA curves provides an effective and useful way to optimize (and monitor) the oxidation condition of a tunneling barrier in MTJs especially of a tunneling barrier less than 10 A thick. The tunneling junctions were also investigated after thermal annealing at various temperatures. The observations after thermal annealing were found to be consistent with transmission electrons microscopy images and a scenario of the partial formation of an additional ultrathin tunneling barrier at the top surface of the bottom magnetic layer

  4. Resonant tunneling through double-barrier structures on graphene

    International Nuclear Information System (INIS)

    Deng Wei-Yin; Zhu Rui; Deng Wen-Ji; Xiao Yun-Chang

    2014-01-01

    Quantum resonant tunneling behaviors of double-barrier structures on graphene are investigated under the tight-binding approximation. The Klein tunneling and resonant tunneling are demonstrated for the quasiparticles with energy close to the Dirac points. The Klein tunneling vanishes by increasing the height of the potential barriers to more than 300 meV. The Dirac transport properties continuously change to the Schrödinger ones. It is found that the peaks of resonant tunneling approximate to the eigen-levels of graphene nanoribbons under appropriate boundary conditions. A comparison between the zigzag- and armchair-edge barriers is given. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  5. Quantum tunneling in the periodically driven SU(2) model

    International Nuclear Information System (INIS)

    Arvieu, R.

    1991-01-01

    The tunneling rate is investigated in the quantum and classical limits using an exactly soluble, periodically driven SU(2) model. The tunneling rate is obtained by solving the time-dependent Schroedinger equation and projecting the exact wave-function on the space of coherent states using the Husimi distribution. The oscillatory, coherent tunneling of the wave-function between two Hartree-Fock minima is observed. The driving plays an important role increasing the tunneling rate by orders of magnitude as compared to the semiclassical results. This is due to the dominant role of excited states in the driven quantum tunneling. (author) 15 refs., 4 figs

  6. Mutual seismic interaction between tunnels and the surrounding granular soil

    Directory of Open Access Journals (Sweden)

    Mohamed Ahmed Abdel-Motaal

    2014-12-01

    Study results show that the maximum exerted straining actions in tunnel lining are directly proportional to the relative stiffness between tunnel and surrounding soil (lining thickness and soil shear modulus. Moreover, it is highly affected by the peak ground acceleration and the tunnel location (embedment depth. A comprehensive study is performed to show the effect of tunnel thickness and tunnel diameter on both the induced bending moment and lining deformation. In general, it is concluded that seismic analysis should be considered in regions subjected to peak ground acceleration greater than 0.15g.

  7. An exact solution for quantum tunneling in a dissipative system

    International Nuclear Information System (INIS)

    Yu, L.H.

    1996-01-01

    Applying a technique developed recently for a harmonic oscillator coupled to a bath of harmonic oscillators, we present an exact solution for the tunneling problem in an Ohmic dissipative system with inverted harmonic potential. The result shows that while the dissipation tends to suppress the tunneling, the Brownian motion tends to enhance the tunneling. Whether the tunneling rate increases or not would then depend on the initial conditions. We give a specific formula to calculate the tunneling probability determined by various parameters and the initial conditions

  8. Spin dynamics in tunneling decay of a metastable state

    OpenAIRE

    Ban, Yue; Sherman, E. Ya.

    2012-01-01

    We analyze spin dynamics in the tunneling decay of a metastable localized state in the presence of spin-orbit coupling. We find that the spin polarization at short time scales is affected by the initial state while at long time scales both the probability- and the spin density exhibit diffraction-in-time phenomenon. We find that in addition to the tunneling time the tunneling in general can be characterized by a new parameter, the tunneling length. Although the tunneling length is independent...

  9. New Method of Sinking Caisson Tunnel in Soft Soil

    OpenAIRE

    Bame, Abda Berisso

    2013-01-01

    Sinking a caisson tunnel in soft soil is new idea and this new concept could be an alternative method of tunneling in soft soil. The aim of this study is to evaluate geotechnical feasibility of sinking the caisson tunnel to the desired depth at the selected soil profile along tunnel alignment. This caisson tunneling method is proposed to reduce the use of temporary works such as propping of sheet pile walls and increase the ease and speed of construction. Besides, it reduces the disturbance o...

  10. Highly doped layer for tunnel junctions in solar cells

    Science.gov (United States)

    Fetzer, Christopher M.

    2017-08-01

    A highly doped layer for interconnecting tunnel junctions in multijunction solar cells is presented. The highly doped layer is a delta doped layer in one or both layers of a tunnel diode junction used to connect two or more p-on-n or n-on-p solar cells in a multijunction solar cell. A delta doped layer is made by interrupting the epitaxial growth of one of the layers of the tunnel diode, depositing a delta dopant at a concentration substantially greater than the concentration used in growing the layer of the tunnel diode, and then continuing to epitaxially grow the remaining tunnel diode.

  11. The comparison between limited open carpal tunnel release using direct vision and tunneling technique and standard open carpal tunnel release: a randomized controlled trial study.

    Science.gov (United States)

    Suppaphol, Sorasak; Worathanarat, Patarawan; Kawinwongkovit, Viroj; Pittayawutwinit, Preecha

    2012-04-01

    To compare the operative outcome of carpal tunnel release between limited open carpal tunnel release using direct vision and tunneling technique (group A) with standard open carpal tunnel release (group B). Twenty-eight patients were enrolled in the present study. A single blind randomized control trial study was conducted to compare the postoperative results between group A and B. The study parameters were Levine's symptom severity and functional score, grip and pinch strength, and average two-point discrimination. The postoperative results between two groups were comparable with no statistical significance. Only grip strength at three months follow up was significantly greater in group A than in group B. The limited open carpal tunnel release in the present study is effective comparable to the standard open carpal tunnel release. The others advantage of this technique are better cosmesis and improvement in grip strength at the three months postoperative period.

  12. Acute Appendicitis

    DEFF Research Database (Denmark)

    Tind, Sofie; Qvist, Niels

    2017-01-01

    and treatment of AA it is important that the classifications are consistent. Furthermore, in the clinical settings, incorrect classification might lead to over diagnosing and a prolonged antibiotic treatment. The aim of our study was to investigate the concordance between perioperative diagnosis made......BACKGROUND: The classification of acute appendicitis (AA) into various grades is not consistent, partly because it is not clear whether the perioperative or the histological findings should be the foundation of the classification. When comparing results from the literature on the frequency...

  13. Resonance tunneling electron-vibrational spectroscopy of polyoxometalates.

    Science.gov (United States)

    Dalidchik, F I; Kovalevskii, S A; Balashov, E M

    2017-05-21

    The tunneling spectra of the ordered monolayer films of decamolybdodicobaltate (DMDC) compounds deposited from aqueous solutions on HOPG were measured by scanning tunnel microscopy in air. The DMDC spectra, as well as the tunneling spectra of other polyoxometalates (POMs), exhibit well-defined negative differential resistances (NDRs). The mechanism of formation of these spectral features was established from the collection of revealed NDR dependences on the external varying parameters and found to be common to all systems exhibiting Wannier-Stark localization. A model of biresonance tunneling was developed to provide an explanation for the totality of experimental data, both the literature and original, on the tunneling POM probing. A variant of the tunneling electron-vibrational POM spectroscopy was proposed allowing the determination of the three basic energy parameters-energy gaps between the occupied and unoccupied states, frequencies of the vibrational transitions accompanying biresonance electron-tunneling processes, and electron-vibrational interaction constants on the monomolecular level.

  14. Cost comparison between Subterrene and current tunneling methods. Final report

    International Nuclear Information System (INIS)

    Bledsoe, J.D.; Hill, J.E.; Coon, R.F.

    1975-05-01

    A study was made to compare tunnel construction costs between the Subterrene tunneling system and methods currently in use. Three completed tunnels were selected for study cases to represent finished diameters ranging from 3.05 meters (10 feet) to 6.25 meters (20.5 feet). The study cases were normalized by deleting extraneous work and assigning labor, equipment, and materials costs for the Southern California area in 1974. Detailed cost estimates (shown in Appendix A) were then made for the three tunnels for baseline. A conceptual nuclear powered Subterrene tunneling machine (NSTM) was designed. It was assumed that NSTM's were available for each of the three baseline tunnels. Costs were estimated (shown in Appendix B) for the baseline tunnels driven by NSTM

  15. Histological Observation of Regions around Bone Tunnels after Compression of the Bone Tunnel Wall in Ligament Reconstruction

    International Nuclear Information System (INIS)

    Maeda, Shintaro; Ishikawa, Hiroki; Tanigawa, Naoaki; Miyazaki, Kyosuke; Shioda, Seiji

    2012-01-01

    The objectives of this study were to investigate the time-course of influence of compression of bone tunnel wall in ligament reconstruction on tissue around the bone tunnel and to histologically examine the mechanism of preventing the complication of bone tunnel dilation, using rabbit tibia. A model in which the femoral origin of the extensor digitorum longus tendon was cut and inserted into a bone tunnel made proximal to the tibia was prepared in the bilateral hind legs of 20 Japanese white rabbits. In each animal, a tunnel was made using a drill only in the right leg, while an undersized bone tunnel was made by drilling and then dilated by compression using a dilator to the same tunnel size as that in the right leg. Animals were sacrificed at 0, 2, 4, 8 and 12 weeks after surgery (4 animals at each time point). Observation of bone tunnels by X-ray radiography showed osteosclerosis in the 2- and 4-week dilation groups. Osteosclerosis appeared as white lines around the bone tunnel on X-ray radiography. This suggests that dilation promotes callus formation in the bone tunnel wall and prevents the complication of bone tunnel enlargement after ligament reconstruction

  16. Spatial effects of Fano resonance in local tunneling conductivity in vicinity of impurity on semiconductor surface

    OpenAIRE

    Mantsevich, V. N.; Maslova, N. S.

    2009-01-01

    We present the results of local tunneling conductivity spatial distribution detailed theoretical investigations in vicinity of impurity atom for a wide range of applied bias voltage. We observed Fano resonance in tunneling conductivity resulting from interference between resonant tunneling channel through impurity energy level and direct tunneling channel between the tunneling contact leads. We have found that interference between tunneling channels strongly modifies form of tunneling conduct...

  17. Tunnel sealing: concept and feasibility evidence

    International Nuclear Information System (INIS)

    Brenner, R.P.; Eppinger, G.; Mettler, K.

    1991-01-01

    This report discusses first the aim and purpose of tunnel seals as well as the requirements which should be satisfied. The basic seal concept is a zoned plug consisting of key zones and intermediate zones. The key zones act as barrier elements and will be placed into sections of competent and sound rock. The main function of the intermediate zones is that of a support and the requirements for sealing efficiency may be somewhat relaxed. Three sealing concepts have been devised for both the key zones and the intermediate zones. They differ in the materials used for the seal and in the placement method. For the key zones highly compacted bentonite is recommended, but also cement-based materials, such as standard concrete or prepact concrete are considered suitable. For the intermediate zones, the use of pumped concrete with subsequent grouting of the roof zone is favourable, but also a combination of concrete with a sand/gravel mixture or with properly compacted excavation material is feasible. The concepts introduced can all be realized by conventional tunnelling methods. Excavation by tunnel boring machine is most advantageous as it minimizes disturbance of the rock caused by the cavity-forming process. By employing simple material models, it can be shown that the depth of the excavation disturbed zone can be minimized if support of the tunnel is provided as early as possible after excavation. The cutting of a groove in the tunnel wall along the key zone can further contribute to reduce the depth of the excavation-disturbed zone. In order to ensure the quality of a seal, the quantities of the materials used can be checked and the work procedures to place the seal can be supervised. For the latter the experiences obtained from a large-scale test should be available. Finally, it is also shown that when considering safety analytical aspects, the proposed sealing concepts represent adequate solutions in spite of the probably increased permeability in the excavation

  18. Acute lower extremity ischaemia

    African Journals Online (AJOL)

    Acute lower extremity ischaemia. Acute lower limb ischaemia is a surgical emergency. ... is ~1.5 cases per 10 000 persons per year. Acute ischaemia ... Table 2. Clinical features discriminating embolic from thrombotic ALEXI. Clinical features.

  19. Acute kidney failure

    Science.gov (United States)

    ... Renal failure - acute; ARF; Kidney injury - acute Images Kidney anatomy References Devarajan P. Biomarkers for assessment of renal function during acute kidney injury. In: Alpern RJ, Moe OW, Caplan M, ...

  20. Fire safety case study of a railway tunnel: Smoke evacuation

    Directory of Open Access Journals (Sweden)

    van Maele Karim

    2007-01-01

    Full Text Available When a fire occurs in a tunnel, it is of great importance to assure the safety of the occupants of the tunnel. This is achieved by creating smoke-free spaces in the tunnel through control of the smoke gases. In this paper, results are presented of a study concerning the fire safety in a real scale railway tunnel test case. Numerical simulations are performed in order to examine the possibility of natural ventilation of smoke in inclined tunnels. Several aspects are taken into account: the length of the simulated tunnel section, the slope of the tunnel and the possible effects of external wind at one portal of the tunnel. The Fire Dynamics Simulator of the National Institute of Standards and Technology, USA, is applied to perform the simulations. The simulations show that for the local behavior of the smoke during the early stages of the fire, the slope of the tunnel is of little importance. Secondly, the results show that external wind and/or pressure conditions have a large effect on the smoke gases inside the tunnel. Finally, some idea for the value of the critical ventilation velocity is given. The study also shows that computational fluid dynamics calculations are a valuable tool for large scale, real life complex fire cases. .

  1. Tunneling anisotropic magnetoresistance driven by magnetic phase transition.

    Science.gov (United States)

    Chen, X Z; Feng, J F; Wang, Z C; Zhang, J; Zhong, X Y; Song, C; Jin, L; Zhang, B; Li, F; Jiang, M; Tan, Y Z; Zhou, X J; Shi, G Y; Zhou, X F; Han, X D; Mao, S C; Chen, Y H; Han, X F; Pan, F

    2017-09-06

    The independent control of two magnetic electrodes and spin-coherent transport in magnetic tunnel junctions are strictly required for tunneling magnetoresistance, while junctions with only one ferromagnetic electrode exhibit tunneling anisotropic magnetoresistance dependent on the anisotropic density of states with no room temperature performance so far. Here, we report an alternative approach to obtaining tunneling anisotropic magnetoresistance in α'-FeRh-based junctions driven by the magnetic phase transition of α'-FeRh and resultantly large variation of the density of states in the vicinity of MgO tunneling barrier, referred to as phase transition tunneling anisotropic magnetoresistance. The junctions with only one α'-FeRh magnetic electrode show a magnetoresistance ratio up to 20% at room temperature. Both the polarity and magnitude of the phase transition tunneling anisotropic magnetoresistance can be modulated by interfacial engineering at the α'-FeRh/MgO interface. Besides the fundamental significance, our finding might add a different dimension to magnetic random access memory and antiferromagnet spintronics.Tunneling anisotropic magnetoresistance is promising for next generation memory devices but limited by the low efficiency and functioning temperature. Here the authors achieved 20% tunneling anisotropic magnetoresistance at room temperature in magnetic tunnel junctions with one α'-FeRh magnetic electrode.

  2. Distribution of tunnelling times for quantum electron transport

    International Nuclear Information System (INIS)

    Rudge, Samuel L.; Kosov, Daniel S.

    2016-01-01

    In electron transport, the tunnelling time is the time taken for an electron to tunnel out of a system after it has tunnelled in. We define the tunnelling time distribution for quantum processes in a dissipative environment and develop a practical approach for calculating it, where the environment is described by the general Markovian master equation. We illustrate the theory by using the rate equation to compute the tunnelling time distribution for electron transport through a molecular junction. The tunnelling time distribution is exponential, which indicates that Markovian quantum tunnelling is a Poissonian statistical process. The tunnelling time distribution is used not only to study the quantum statistics of tunnelling along the average electric current but also to analyse extreme quantum events where an electron jumps against the applied voltage bias. The average tunnelling time shows distinctly different temperature dependence for p- and n-type molecular junctions and therefore provides a sensitive tool to probe the alignment of molecular orbitals relative to the electrode Fermi energy.

  3. Scanning Tunneling Spectroscopy of Potassium on Graphene

    Science.gov (United States)

    Cormode, Daniel; Leroy, Brian; Yankowitz, Matthew

    2012-02-01

    We investigate the effect of charged impurities on the electronic properties of large single crystal CVD grown graphene using scanning tunneling microscopy. Mono- and multilayer crystals were prepared by transferring graphene from copper onto exfoliated boron nitride flakes on 300 nm SiO2 substrates. The boron nitride provides an ultra flat surface for the graphene. Potassium atoms are controllably deposited on the graphene at low temperature by heating a nearby getter source. Scanning tunneling spectroscopy and transport measurements were performed in ultra high vacuum at 4.5 K. Transport measurements demonstrate the shifting of the Dirac point as the samples are doped, while STM measurements demonstrate the size, arrangement and local electronic influence of the potassium atoms.

  4. Convexity, gauge-dependence and tunneling rates

    Energy Technology Data Exchange (ETDEWEB)

    Plascencia, Alexis D.; Tamarit, Carlos [Institute for Particle Physics Phenomenology, Durham University,South Road, DH1 3LE (United Kingdom)

    2016-10-19

    We clarify issues of convexity, gauge-dependence and radiative corrections in relation to tunneling rates. Despite the gauge dependence of the effective action at zero and finite temperature, it is shown that tunneling and nucleation rates remain independent of the choice of gauge-fixing. Taking as a starting point the functional that defines the transition amplitude from a false vacuum onto itself, it is shown that decay rates are exactly determined by a non-convex, false vacuum effective action evaluated at an extremum. The latter can be viewed as a generalized bounce configuration, and gauge-independence follows from the appropriate Nielsen identities. This holds for any election of gauge-fixing that leads to an invertible Faddeev-Popov matrix.

  5. Single-electron tunnel junction array

    International Nuclear Information System (INIS)

    Likharev, K.K.; Bakhvalov, N.S.; Kazacha, G.S.; Serdyukova, S.I.

    1989-01-01

    The authors have carried out an analysis of statics and dynamics of uniform one-dimensional arrays of ultrasmall tunnel junctions. The correlated single-electron tunneling in the junctions of the array results in its behavior qualitatively similar to that of the Josephson transmission line. In particular, external electric fields applied to the array edges can inject single-electron-charged solitons into the array interior. Shape of such soliton and character of its interactions with other solitons and the array edges are very similar to those of the Josephson vortices (sine-Gordon solitons) in the Josephson transmission line. Under certain conditions, a coherent motion of the soliton train along the array is possible, resulting in generation of narrowband SET oscillations with frequency f/sub s/ = /e where is the dc current flowing along the array

  6. Photogrammetry Applied to Wind Tunnel Testing

    Science.gov (United States)

    Liu, Tian-Shu; Cattafesta, L. N., III; Radeztsky, R. H.; Burner, A. W.

    2000-01-01

    In image-based measurements, quantitative image data must be mapped to three-dimensional object space. Analytical photogrammetric methods, which may be used to accomplish this task, are discussed from the viewpoint of experimental fluid dynamicists. The Direct Linear Transformation (DLT) for camera calibration, used in pressure sensitive paint, is summarized. An optimization method for camera calibration is developed that can be used to determine the camera calibration parameters, including those describing lens distortion, from a single image. Combined with the DLT method, this method allows a rapid and comprehensive in-situ camera calibration and therefore is particularly useful for quantitative flow visualization and other measurements such as model attitude and deformation in production wind tunnels. The paper also includes a brief description of typical photogrammetric applications to temperature- and pressure-sensitive paint measurements and model deformation measurements in wind tunnels.

  7. Review of Potential Wind Tunnel Balance Technologies

    Science.gov (United States)

    Burns, Devin E.; Williams, Quincy L.; Phillips, Ben D.; Commo, Sean A.; Ponder, Jonathon D.

    2016-01-01

    This manuscript reviews design, manufacture, materials, sensors, and data acquisition technologies that may benefit wind tunnel balances for the aerospace research community. Current state-of-the-art practices are used as the benchmark to consider advancements driven by researcher and facility needs. Additive manufacturing is highlighted as a promising alternative technology to conventional fabrication and has the potential to reduce both the cost and time required to manufacture force balances. Material alternatives to maraging steels are reviewed. Sensor technologies including piezoresistive, piezoelectric, surface acoustic wave, and fiber optic are compared to traditional foil based gages to highlight unique opportunities and shared challenges for implementation in wind tunnel environments. Finally, data acquisition systems that could be integrated into force balances are highlighted as a way to simplify the user experience and improve data quality. In summary, a rank ordering is provided to support strategic investment in exploring the technologies reviewed in this manuscript.

  8. Tunneling spectra of graphene on copper unraveled

    DEFF Research Database (Denmark)

    Zhang, Xin; Stradi, Daniele; Liu, Lei

    2016-01-01

    mechanisms, etc. The interpretation of the spectra can be complicated, however. Specifically for graphene grown on copper, there have been conflicting reports of tunneling spectra. A clear understanding of the mechanisms behind the variability is desired. In this work, we have revealed that the root cause...... of the variability in tunneling spectra is the variation in graphene-substrate coupling under various experimental conditions, providing a salutary perspective on the important role of 2D material-substrate interactions. The conclusions are drawn from measured data and theoretical calculations for monolayer, AB......-stacked bilayer, and twisted bilayer graphene coexisting on the same substrates in areas with and without intercalated oxygen, demonstrating a high degree of consistency. The Van Hove singularities of the twisted graphene unambiguously indicate the Dirac energy between them, lending strong evidence to our...

  9. View of the LHC tunnel with worker.

    CERN Multimedia

    Maximilien Brice

    2006-01-01

    The 616th dipole out of 1232, on its way to its final position in the tunnel of the LHC. Technicians and engineers continue to work day and night carefully installing 20 magnets a week. Each of the dipoles weighs 34 tonnes and is 15 m long. Once they have been lowered down the specially constructed shaft on the Meyrin site, they begin a slow progression to their final destinations in the LHC tunnel, taking about 10 hours to arrive at Point 6, the furthest point on the LHC ring. Upon arrival, each of the dipoles is aligned and interconnected to the magnets that are already installed.Bigger files available (39Mpx)

  10. Scanning tunneling microscope assembly, reactor, and system

    Science.gov (United States)

    Tao, Feng; Salmeron, Miquel; Somorjai, Gabor A

    2014-11-18

    An embodiment of a scanning tunneling microscope (STM) reactor includes a pressure vessel, an STM assembly, and three spring coupling objects. The pressure vessel includes a sealable port, an interior, and an exterior. An embodiment of an STM system includes a vacuum chamber, an STM reactor, and three springs. The three springs couple the STM reactor to the vacuum chamber and are operable to suspend the scanning tunneling microscope reactor within the interior of the vacuum chamber during operation of the STM reactor. An embodiment of an STM assembly includes a coarse displacement arrangement, a piezoelectric fine displacement scanning tube coupled to the coarse displacement arrangement, and a receiver. The piezoelectric fine displacement scanning tube is coupled to the coarse displacement arrangement. The receiver is coupled to the piezoelectric scanning tube and is operable to receive a tip holder, and the tip holder is operable to receive a tip.

  11. Atomic physics with the scanning tunneling microscope

    International Nuclear Information System (INIS)

    Kleber, M.; Bracher, C.; Riza, M.

    1999-01-01

    Backscattering of atomic beams above a given surface yields information similar to the one obtained from scanning the same surface with a scanning tunneling microscope (STM): In both cases the experimentally accessible quantity is the local density of states (LDOS) n(r,E) of the surface. For the case of backscattering, the LDOS at the turning point of the atom is an important ingredient of the potential between atom and surface. In experiments performed with an STM, the LDOS at the apex of an atomically sharp tip can be determined directly. Probing surfaces locally by an STM allows for the study of basic phenomena in atomic physics, with tunneling of electrons in three dimensions being a central issue

  12. Structural and tunneling properties of Si nanowires

    KAUST Repository

    Montes Muñoz, Enrique

    2013-12-06

    We investigate the electronic structure and electron transport properties of Si nanowires attached to Au electrodes from first principles using density functional theory and the nonequilibrium Green\\'s function method. We systematically study the dependence of the transport properties on the diameter of the nanowires, on the growth direction, and on the length. At the equilibrium Au-nanowire distance we find strong electronic coupling between the electrodes and nanowires, which results in a low contact resistance. With increasing nanowire length we study the transition from metallic to tunneling conductance for small applied bias. For the tunneling regime we investigate the decay of the conductance with the nanowire length and rationalize the results using the complex band structure of the pristine nanowires. The conductance is found to depend strongly on the growth direction, with nanowires grown along the ⟨110⟩ direction showing the smallest decay with length and the largest conductance and current.

  13. Tunneling of heat: Beyond linear response regime

    Science.gov (United States)

    Walczak, Kamil; Saroka, David

    2018-02-01

    We examine nanoscale processes of heat (energy) transfer as carried by electrons tunneling via potential barriers and molecular interconnects between two heat reservoirs (thermal baths). For that purpose, we use Landauer-type formulas to calculate thermal conductance and quadratic correction to heat flux flowing via quantum systems. As an input, we implement analytical expressions for transmission functions related to simple potential barriers and atomic bridges. Our results are discussed with respect to energy of tunneling electrons, temperature, the presence of resonant states, and specific parameters characterizing potential barriers as well as heat carriers. The simplicity of semi-analytical models developed by us allows to fit experimental data and extract crucial information about the values of model parameters. Further investigations are expected for more realistic transmission functions, while time-dependent aspects of nanoscale heat transfer may be addressed by using the concept of wave packets scattered on potential barriers and point-like defects within regular (periodic) nanostructures.

  14. Tunnel backfill erosion by dilute water

    Energy Technology Data Exchange (ETDEWEB)

    Olin, M. [VTT Technical Research Centre of Finland, Espoo (Finland)

    2014-03-15

    The goal was to estimate smectite release from tunnel backfill due to dilute groundwater pulse during post glacial conditions. The plan was to apply VTT's two different implementations (BESW{sub D} and BESW{sub S}) of well-known model of Neretnieks et al. (2009). It appeared difficult to produce repeatable results using this model in COMSOL 4.2 environment, therefore a semi-analytical approximate approach was applied, which enabled to take into account both different geometry and smectite content in tunnel backfill as compared to buffer case. The results are quite similar to buffer results due to the decreasing effect of smaller smectite content and the increasing effect of larger radius. (orig.)

  15. Tunnel backfill erosion by dilute water

    International Nuclear Information System (INIS)

    Olin, M.

    2014-03-01

    The goal was to estimate smectite release from tunnel backfill due to dilute groundwater pulse during post glacial conditions. The plan was to apply VTT's two different implementations (BESW D and BESW S ) of well-known model of Neretnieks et al. (2009). It appeared difficult to produce repeatable results using this model in COMSOL 4.2 environment, therefore a semi-analytical approximate approach was applied, which enabled to take into account both different geometry and smectite content in tunnel backfill as compared to buffer case. The results are quite similar to buffer results due to the decreasing effect of smaller smectite content and the increasing effect of larger radius. (orig.)

  16. Delay time and tunneling transient phenomena

    International Nuclear Information System (INIS)

    Garcia-Calderon, Gaston; Villavicencio, Jorge

    2002-01-01

    Analytic solutions to the time-dependent Schroedinger equation for cutoff wave initial conditions are used to investigate the time evolution of the transmitted probability density for tunneling. For a broad range of values of the potential barrier opacity α, we find that the probability density exhibits two evolving structures. One refers to the propagation of a forerunner related to a time domain resonance [Phys. Rev. A 64, 0121907 (2001)], while the other consists of a semiclassical propagating wave front. We find a regime where the forerunners are absent, corresponding to positive time delays, and show that this regime is characterized by opacities α c . The critical opacity α c is derived from the analytical expression for the delay time, which reflects a link between transient effects in tunneling and the delay time

  17. Alternative diagnostic technique for carpal tunnel syndrome

    International Nuclear Information System (INIS)

    Hayakawa, Katsuhiko; Nakane, Takashi; Kobayashi, Shigeru; Shibata, Kunio

    2002-01-01

    Compressive and entrapment neuropathies are common clinical syndromes characterized by neurologic deficits due to mechanical or dynamic compression of peripheral nerves. However, the definitive diagnosis based on clinical symptoms alone is difficult in many cases, and the electrophysiological diagnostic method is solely used as a supplementary diagnostic method at present. As a new diagnostic method for entrapment neuropathy, the present study investigated the usefulness of gadolinium-enhanced MRI in carpal tunnel syndrome. On enhanced MRI of idiopathic carpal tunnel syndrome, contrast-enhancement in the median nerve was found in 30 of 34 hands (88.2%). Enhanced MRI allows to visualize intraneural edema in the nerve easily on the naked eye. Therefore, this technique supplied useful information for making definitive diagnosis and is promising as a non-invasive diagnostic method for entrapment neuropathy. (author)

  18. Construction of tunnel Bôrik

    Directory of Open Access Journals (Sweden)

    Jozef Čížik

    2009-09-01

    Full Text Available When tunneling engineers talk on NATM, they often mean different things because some of them define it as a special technique,but others as a sort of philosophy. Recently the scene has been complicated by new terms and even alternative names, when discussingcertain aspects of NATM.The NATM integrates the principles of the behaviour of rock masses under load and monitoring the performance of undergroundconstruction during construction. The NATM is not a set of specific excavation and support techniques. Based on the computationof the optimal cross section, just a thin shotcrete protection is necessary. Additionally, geotechnical instruments are installed to measurethe later deformation of excavation. Therefore a monitoring of the stress distribution within the rock is possible. This monitoring makesthe method very flexible, even at surprising changes of the geomechanical rock consistency during the tunneling work.

  19. Cryogenic Wind Tunnel Models. Design and Fabrication

    Science.gov (United States)

    Young, C. P., Jr. (Compiler); Gloss, B. B. (Compiler)

    1983-01-01

    The principal motivating factor was the National Transonic Facility (NTF). Since the NTF can achieve significantly higher Reynolds numbers at transonic speeds than other wind tunnels in the world, and will therefore occupy a unique position among ground test facilities, every effort is being made to ensure that model design and fabrication technology exists to allow researchers to take advantage of this high Reynolds number capability. Since a great deal of experience in designing and fabricating cryogenic wind tunnel models does not exist, and since the experience that does exist is scattered over a number of organizations, there is a need to bring existing experience in these areas together and share it among all interested parties. Representatives from government, the airframe industry, and universities are included.

  20. Alternative diagnostic technique for carpal tunnel syndrome

    Energy Technology Data Exchange (ETDEWEB)

    Hayakawa, Katsuhiko; Nakane, Takashi [Aiko Orthopaedic Hospital, Nagoya (Japan); Kobayashi, Shigeru; Shibata, Kunio [Fujita Health Univ., Toyoake, Aichi (Japan). School of Medicine

    2002-10-01

    Compressive and entrapment neuropathies are common clinical syndromes characterized by neurologic deficits due to mechanical or dynamic compression of peripheral nerves. However, the definitive diagnosis based on clinical symptoms alone is difficult in many cases, and the electrophysiological diagnostic method is solely used as a supplementary diagnostic method at present. As a new diagnostic method for entrapment neuropathy, the present study investigated the usefulness of gadolinium-enhanced MRI in carpal tunnel syndrome. On enhanced MRI of idiopathic carpal tunnel syndrome, contrast-enhancement in the median nerve was found in 30 of 34 hands (88.2%). Enhanced MRI allows to visualize intraneural edema in the nerve easily on the naked eye. Therefore, this technique supplied useful information for making definitive diagnosis and is promising as a non-invasive diagnostic method for entrapment neuropathy. (author)