Exciton Condensation and Perfect Coulomb Drag

Coulomb drag is a process whereby the repulsive interactions between electrons in spatially separated conductors enable a current flowing in one of the conductors to induce a voltage drop in the other. If the second conductor is part of a closed circuit, a net current will flow in that circuit. The drag current is typically much smaller than the drive current owing to the heavy screening of the Coulomb interaction. There are, however, rare situations in which strong electronic correlations exist between the two conductors. For example, bilayer two-dimensional electron systems can support an exciton condensate consisting of electrons in one layer tightly bound to holes in the other. One thus expects "perfect" drag; a transport current of electrons driven through one layer is accompanied by an equal one of holes in the other. (The electrical currents are therefore opposite in sign.) Here we demonstrate just this effect, taking care to ensure that the electron-hole pairs dominate the transport and that tunneling of charge between the layers is negligible.Comment: 12 pages, 4 figure

Transcriptional control in the prereplicative phase of T4 development

Control of transcription is crucial for correct gene expression and orderly development. For many years, bacteriophage T4 has provided a simple model system to investigate mechanisms that regulate this process. Development of T4 requires the transcription of early, middle and late RNAs. Because T4 does not encode its own RNA polymerase, it must redirect the polymerase of its host, E. coli, to the correct class of genes at the correct time. T4 accomplishes this through the action of phage-encoded factors. Here I review recent studies investigating the transcription of T4 prereplicative genes, which are expressed as early and middle transcripts. Early RNAs are generated immediately after infection from T4 promoters that contain excellent recognition sequences for host polymerase. Consequently, the early promoters compete extremely well with host promoters for the available polymerase. T4 early promoter activity is further enhanced by the action of the T4 Alt protein, a component of the phage head that is injected into E. coli along with the phage DNA. Alt modifies Arg265 on one of the two α subunits of RNA polymerase. Although work with host promoters predicts that this modification should decrease promoter activity, transcription from some T4 early promoters increases when RNA polymerase is modified by Alt. Transcription of T4 middle genes begins about 1 minute after infection and proceeds by two pathways: 1) extension of early transcripts into downstream middle genes and 2) activation of T4 middle promoters through a process called sigma appropriation. In this activation, the T4 co-activator AsiA binds to Region 4 of σ70, the specificity subunit of RNA polymerase. This binding dramatically remodels this portion of σ70, which then allows the T4 activator MotA to also interact with σ70. In addition, AsiA restructuring of σ70 prevents Region 4 from forming its normal contacts with the -35 region of promoter DNA, which in turn allows MotA to interact with its DNA binding site, a MotA box, centered at the -30 region of middle promoter DNA. T4 sigma appropriation reveals how a specific domain within RNA polymerase can be remolded and then exploited to alter promoter specificity

Modified triangular posterior osteosynthesis of unstable sacrum fracture.

We report preliminary results for unstable sacral fractures treated with a modified posterior triangular osteosynthesis. Seven patients were admitted to our trauma center with an unstable sacral fracture. The average age was 31 years (22-41). There were four vertical shear lesions of the pelvis and three transverse fracture of the upper sacrum. The vertical shear injuries were initially treated with an anterior external fixator inserted at the time of admission. Definitive surgery was performed at a mean time of 9 days after trauma. The operation consisted in a posterior fixation combining a vertebropelvic distraction osteosynthesis with pedicle screws and a rod system, whereby the transverse fixation was obtained using a 6 mm rod as a cross-link between the two main rods. Late displacement of the posterior pelvis or fracture was measured on X-ray films according to the criteria of Henderson. The patients were followed-up for a minimum time of 12 months. Four patients who presented with a pre-operative perineal neurological impairment made a complete recovery. No iatrogenic nerve injury was reported. One case of deep infection was managed successfully with surgical debridement and local antibiotics. All patients complained of symptoms related to the prominence of the iliac screws. The metalwork was removed in all cases after healing of the fracture, at a mean time of 4.3 months after surgery. No loss of reduction of fracture was seen at final radiological follow-up. The preliminary results are promising. The fixation is sufficiently stable to allow an immediate progressive weight-bearing, and safe nursing care in polytrauma cases. The only problem seems to be related to prominent heads of the distal screws

Pelvic trauma : WSES classification and guidelines

Complex pelvic injuries are among the most dangerous and deadly trauma related lesions. Different classification systems exist, some are based on the mechanism of injury, some on anatomic patterns and some are focusing on the resulting instability requiring operative fixation. The optimal treatment strategy, however, should keep into consideration the hemodynamic status, the anatomic impairment of pelvic ring function and the associated injuries. The management of pelvic trauma patients aims definitively to restore the homeostasis and the normal physiopathology associated to the mechanical stability of the pelvic ring. Thus the management of pelvic trauma must be multidisciplinary and should be ultimately based on the physiology of the patient and the anatomy of the injury. This paper presents the World Society of Emergency Surgery (WSES) classification of pelvic trauma and the management Guidelines.Peer reviewe

Vampires in the village Žrnovo on the island of Korčula: following an archival document from the 18th century

Središnja tema rada usmjerena je na raščlambu spisa pohranjenog u Državnom arhivu u Mlecima (fond: Capi del Consiglio de’ Dieci: Lettere di Rettori e di altre cariche) koji se odnosi na događaj iz 1748. godine u korčulanskom selu Žrnovo, kada su mještani – vjerujući da su se pojavili vampiri – oskvrnuli nekoliko mjesnih grobova. U radu se podrobno iznose osnovni podaci iz spisa te rečeni događaj analizira u širem društvenom kontekstu i prate se lokalna vjerovanja.The main interest of this essay is the analysis of the document from the State Archive in Venice (file: Capi del Consiglio de’ Dieci: Lettere di Rettori e di altre cariche) which is connected with the episode from 1748 when the inhabitants of the village Žrnove on the island of Korčula in Croatia opened tombs on the local cemetery in the fear of the vampires treating. This essay try to show some social circumstances connected with this event as well as a local vernacular tradition concerning superstitions

Kniearthrodese - Ultima Ratio bei der Behandlung des infizierten Kniegelenkes

The irretrievable destruction of the knee due to trauma, tumor or infection is the indication for knee arthrodesis. The main reason for knee arthrodesis in terms of infection ist the infected total knee arthroplasty. Central problem is the definition of the term "irretrievable". It is based on the subjective opinion of the attending physician and depends on his expert knowledge of this specific entity. The preservation of a functioning extremity is the main goal.This article shows the typical indications and contraindications for knee arthrodesis following septic knee diseases. In addition it gives insight into the biomechanical and technical considerations to be kept in mind. Finally the postoperative care and outcome of different techniques are analysed.Die unwiderrufliche Zerstörung des Kniegelenkes durch Trauma, Tumor oder Infektion stellt die Indikation zur Kniearthrodese dar. Die Hautpindikation zur Kniearthrodese besteht im Zusammenhang mit irreversibel zerstörten Knieendoprothesen.Zentrales Problem bei der Indikationsstetllung ist der Begriff "unwiederbringliche Zerstörung". Die Einschätzung einer derartigen Situation basiert auf dem subjektiven Empfinden des behandelnden Arztes und seiner Erfahrung auf diesem Gebiet.Dieser Artikel zeigt die typischen Indikationen und Kontraindikationen zur Kniearthrodese nach infektbedingter Zerstörung des Kniegelenkes auf. Zusätzlich werden biomechanische und operationstechnische Aspekte beleuchtet. Abschließend werden die postoperative Nachbehandlung und die Ergebnisse unterschiedlicher Methoden beschrieben

Reconstructive surgery in case of musculoskeletal infections - what about osteomyelitis

Osteomyelitis therapy is based on defined principles and may be subdivided into three phases: Sanitation and sedation of the infect (bone plus soft tissue) Soft tissue reconstruction Skeletal reconstruction Depending on the local situation phase two and three may be performed together. The following article gives a brief review how to act in the specific above named phases