Macroscopic coherence effects in a mesoscopic system: Weak localization of thin silver films in an undergraduate lab

We present an undergraduate lab that investigates weak localization in thin silver films. The films prepared in our lab have thickness, $a$, between 60-200 \AA, a mesoscopic length scale. At low temperatures, the inelastic dephasing length for electrons, $L_{\phi}$, exceeds the thickness of the film ($L_{\phi} \gg a$), and the films are then quasi-2D in nature. In this situation, theory predicts specific corrections to the Drude conductivity due to coherent interference between conducting electrons' wavefunctions, a macroscopically observable effect known as weak localization. This correction can be destroyed with the application of a magnetic field, and the resulting magnetoresistance curve provides information about electron transport in the film. This lab is suitable for Junior or Senior level students in an advanced undergraduate lab course.Comment: 16 pages, 9 figures. Replaces earlier version of paper rejected by Am. J. Phys. because of too much content on vacuum systems. New version deals with the undergraduate experiment on weak localization onl

Decreased cardiac excitability secondary to reduction of sodium current may be a significant contributor to reduced contractility in a rat model of sepsis

Pembelajaran pada hakekatnya adalah proses interaksi antara peserta didik dengan lingkungannya. Pembelajaran merupakan aktualisasi kurikulum yang menuntut keaktifan guru dalam menciptakan dan menumbuhkan kegiatan peserta didik sesuai dengan rencana yang telah diprogramkan. Dalam pembelajaran matematika sering kita temui adanya siswa yang kesulitan dalam menerima materi yang diajarkan, untuk mengantisipasi hal itu pembelajaran matematika hendaknya dimulai dengan pengenalan masalah yang sesuai dengan situasi (contextual problem). Salah satu pendekatan yang sesuai untuk menunjang guru sebagai guru profesional adalah pendekatan PMRI, sehingga siswa bisa mengkonstruksi pengetahuannya sendiri. Rumusan masalah yang diteliti dalam penelitian ini adalah bagaimana mengembangkan bahan ajar yang valid dan praktis yang dikembangkan dengan pendekatan PMRI, dan bagaimana efek potensial bahan ajar yang dikembangkan dengan pendekatan PMRI terhadap hasil belajar siswa. Penelitian ini merupakan penelitian pengembangan (development research) yang bertujuan untuk menghasilkan bahan ajar yang valid, praktis dan efektif untuk pembelajaran matematika di kelas VII SMP Negeri 4 Pangkal Pinang. Subjek penelitian ini adalah siswa kelas VII.D sebanyak 36 siswa. Dengan kesimpulan bahwa bahan ajar yang dikembangkan dalam penelitian ini dikategorikan valid, praktis dan memiliki potential effect terhadap hasil belajar siswa di kelas VII.D SMP Negeri 4 Pangkal Pinang. Kata kunci : himpunan, pendekatan PMRI DOI: http://dx.doi.org/10.22342/jpm.8.1.1859.43-5

Genomic sequencing capacity, data retention, and personal access to raw data in Europe

Whole genome/exome sequencing (WGS/WES) has become widely adopted in research and, more recently, in clinical settings. Many hope that the information obtained from the interpretation of these data will have medical benefits for patients and—in some cases—also their biological relatives. Because of the manifold possibilities to reuse genomic data, enabling sequenced individuals to access their own raw (uninterpreted) genomic data is a highly debated issue. This paper reports some of the first empirical findings on personal genome access policies and practices. We interviewed 39 respondents, working at 33 institutions in 21 countries across Europe. These sequencing institutions generate massive amounts of WGS/WES data and represent varying organisational structures and operational models. Taken together, in total, these institutions have sequenced ∼317,259 genomes and exomes to date. Most of the sequencing institutions reported that they are able to store raw genomic data in compliance with various national regulations, although there was a lack of standardisation of storage formats. Interviewees from 12 of the 33 institutions included in our study reported that they had received requests for personal access to raw genomic data from sequenced individuals. In the absence of policies on how to process such requests, these were decided on an ad hoc basis; in the end, at least 28 requests were granted, while there were no reports of requests being rejected. Given the rights, interests, and liabilities at stake, it is essential that sequencing institutions adopt clear policies and processes for raw genomic data retention and personal access

Homeostatic Synaptic Plasticity of Miniature Excitatory Postsynaptic Currents in Mouse Cortical Cultures Requires Neuronal Rab3A

Following prolonged activity blockade, amplitudes of miniature excitatory postsynaptic currents (mEPSCs) increase, a form of homeostatic plasticity termed “synaptic scaling.” We previously showed that a presynaptic protein, the small GTPase Rab3A, is required for full expression of the increase in miniature endplate current amplitudes following prolonged blockade of action potential activity at the mouse neuromuscular junction in vivo (Wang et al., 2011), but it is unknown whether this form of Rab3A-dependent homeostatic plasticity shares any characteristics with central synapses. We show here that synaptic scaling of mEPSCs is impaired in mouse cortical neuron cultures prepared from Rab3A-/- and Rab3A Earlybird mutant mice. To determine if Rab3A is involved in the well-established homeostatic increase in postsynaptic AMPA-type receptors (AMPARs), we performed a series of experiments in which electrophysiological recordings of mEPSCs and confocal imaging of synaptic AMPAR immunofluorescence were assessed within the same cultures. We found that Rab3A is required for the increase in synaptic AMPARs following prolonged activity blockade, but the comparison of mEPSC amplitude and synaptic AMPARs in the same cultures revealed that mEPSC amplitude cannot solely be determined by postsynaptic AMPAR levels. Finally, we demonstrate that Rab3A is acting in neurons because selective loss of Rab3A in astrocytes did not disrupt homeostatic plasticity, whereas selective loss in neurons strongly reduced the homeostatic increase in mEPSC amplitudes. Taken together with the results at the neuromuscular junction, we propose that Rab3A is a presynaptic homeostatic regulator that controls quantal size on both sides of the synapse

SLC2A9 (GLUT9) mediates urate reabsorption in the mouse kidney.

Uric acid (UA) is a metabolite of purine degradation and is involved in gout flairs and kidney stones formation. GLUT9 (SLC2A9) was previously shown to be a urate transporter in vitro. In vivo, humans carrying GLUT9 loss-of-function mutations have familial renal hypouricemia type 2, a condition characterized by hypouricemia, UA renal wasting associated with kidney stones, and an increased propensity to acute renal failure during strenuous exercise. Mice carrying a deletion of GLUT9 in the whole body are hyperuricemic and display a severe nephropathy due to intratubular uric acid precipitation. However, the precise role of GLUT9 in the kidney remains poorly characterized. We developed a mouse model in which GLUT9 was deleted specifically along the whole nephron in a tetracycline-inducible manner (subsequently called kidney-inducible KO or kiKO). The urate/creatinine ratio was increased as early as 4 days after induction of the KO and no GLUT9 protein was visible on kidney extracts. kiKO mice are morphologically identical to their wild-type littermates and had no spontaneous kidney stones. Twenty-four-hour urine collection revealed a major increase of urate urinary excretion rate and of the fractional excretion of urate, with no difference in urate concentration in the plasma. Polyuria was observed, but kiKO mice were still able to concentrate urine after water restriction. KiKO mice displayed lower blood pressure accompanied by an increased heart rate. Overall, these results indicate that GLUT9 is a crucial player in renal handling of urate in vivo and a putative target for uricosuric drugs

The Mechanism Underlying Transient Weakness in Myotonia Congenita

In addition to the hallmark muscle stiffness, patients with recessive myotonia congenita (Becker disease) experience debilitating bouts of transient weakness that remain poorly understood despite years of study. We performed intracellular recordings from muscle of both genetic and pharmacologic mouse models of Becker disease to identify the mechanism underlying transient weakness. Our recordings reveal transient depolarizations (plateau potentials) of the membrane potential to -25 to -35 mV in the genetic and pharmacologic models of Becker disease. Both Na + and Ca 2+ currents contribute to plateau potentials. Na + persistent inward current (NaPIC) through Na V 1.4 channels is the key trigger of plateau potentials and current through Ca V 1.1 Ca 2+ channels contributes to the duration of the plateau. Inhibiting NaPIC with ranolazine prevents the development of plateau potentials and eliminates transient weakness in vivo. These data suggest that targeting NaPIC may be an effective treatment to prevent transient weakness in myotonia congenita

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Publicat a La Voz de Asturias

Forty-five years of schizophrenia trials in Italy: a survey

<p>Abstract</p> <p>Background</p> <p>Well-designed and properly executed randomized controlled trials (RCTs) provide the best evidence on the efficacy of healthcare interventions. Mental health has a strong tradition of using trial to evaluate treatments, but the translation of research to clinical practice is not always easy. Even well-conducted trials do not necessarily address the needs of every day care and trials can reflect local needs and the specific culture in which they are undertaken. Generalizing results to other contexts can become problematic but these trials may, nevertheless, be very helpful within their own context. Moreover, pathways for drug approval can be different depending on local regulatory agencies. Local trials are helpful for decision-making in the region from which they come, but should not be viewed in isolation. National quantity and quality of trials may vary across nations.</p> <p>The aim of this study is to quantify trialing activity in Italy from 1948 until 2009 and to describe characteristics of these trials. In addition, we evaluated change over time in three keys aspects: sample size, follow-up duration, and number of outcomes.</p> <p>Methods</p> <p>We used the Cochrane Schizophrenia Group's register that contains 16,000 citations to 13,000 studies relating only to people with schizophrenia or schizophrenia-like illness. Randomized controlled trials and controlled clinical trials undertaken in Italy and involving pharmacological interventions were included.</p> <p>Results</p> <p>The original search identified 155 records of potentially eligible studies, 74 of which were excluded because do not meet inclusion criteria. A total of 81 studies were included in the analysis. The majority of trials were conducted in north Italy, and published in international journals between 1981 and 1995. The majority of studies (52 out of 81) used standardized diagnostic criteria for schizophrenia disorder. They were defined as randomized and used blind methods to administer treatment. However, most failed to report detail regarding methodological procedures and it is difficult to ascertain which studies are associated with a low risk of bias.</p> <p>Conclusions</p> <p>Trials should be designed to address the needs of everyday care with the aim of following large samples of typical patients in the long term. The Italian tradition in the area of trialing treatments for people with schizophrenia is not as strong as in many other similar countries and Italy should be producing more, better, independent, and clinically relevant trials.</p