Transport spectroscopy of symmetry-broken insulating states in bilayer graphene

Bilayer graphene is an attractive platform for studying new two-dimensional electron physics, because its flat energy bands are sensitive to out-of-plane electric fields and these bands magnify electron-electron interaction effects. Theory predicts a variety of interesting broken symmetry states when the electron density is at the carrier neutrality point, and some of these states are characterized by spontaneous mass gaps, which lead to insulating behaviour. These proposed gaps are analogous to the masses generated by broken symmetries in particle physics, and they give rise to large Berry phase effects accompanied by spontaneous quantum Hall effects. Although recent experiments have provided evidence for strong electronic correlations near the charge neutrality point, the presence of gaps remains controversial. Here, we report transport measurements in ultraclean double-gated bilayer graphene and use source-drain bias as a spectroscopic tool to resolve a gap of ∼2 meV at the charge neutrality point. The gap can be closed by a perpendicular electric field of strength ∼15 mV nm(-1), but it increases monotonically with magnetic field, with an apparent particle-hole asymmetry above the gap. These data represent the first spectroscopic mapping of the ground states in bilayer graphene in the presence of both electric and magnetic fields.

T cell signal transduction and the role of CD7 in costimulation

The complex cellular interactions that govern the mammalian immune response are now known to include specific receptor/ligand interactions, recruitment of intracellular signaling molecules, activation of both kinases and phosphatases, and redistribution of macromolecular complexes into specific subcellular membrane locations that, in aggregate, result in transcriptional activation. While the TCR-CD3 signal is critical for activation of the resting T cell, it alone is not sufficient to initiate transcriptional activation or generate an effective immune response. A number of other coreceptor molecules, including CD4, CD8, and CD28, have now been characterized that also play important roles in initiating or amplifying the activation of the T cell. A 40 kDa member of the immunoglobulin superfamily, the CD7 molecule, has also been shown to have costimulatory activity and to induce tyrosine and lipid kinase activities. Here we will review the signaling pathways initiated by TCR, CD28, and CD7, as well as the functional consequences of signal transduction through these receptors.

First experimental sutureless laser anastomosis of the large bowel: long-term study

Large bowel anastomoses were successfully performed without sutures on New Zealand white rabbits using 1,064 nm, 0.4-W power pulsating Nd:YAG laser to create tissue welding.

PURPOSE

The aim of this study was to assess long-term results of our experimental data and summarize our experimental work on laser colon anastomosis.

METHODS

This experimental study investigated long-term integrity, degree of narrowing, animal body weight change, visual findings, microscopic appearance, and collagen concentration of laser colon anastomoses, compared with those of conventional sutured anastomoses at thirty and ninety postoperative days.

RESULTS

Two animals in the laser group died without leakage. Postsurgical course in all remaining rabbits studied was uneventful. Bursting pressures in the two groups were equivalent, but the laser group exhibited a consistent narrowing tendency. However, laser anastomoses demonstrated fewer and milder adhesions, and animals showed a better recovery of body weight. Histologically, laser anastomoses showed better layer-to-layer reconstitution without foreign body response and with less fibrosis. Difference in collagen (hydroxyproline) concentration did not reach statistical significance.

CONCLUSION

The nature of tissue welding via laser remains undefined, but there is definitely a future for laser bowel anastomosis.

The SH2 domains of Src family kinases associate with Syk

Src family kinases (Lyn, Fyn, Lck, and Blk) and Syk, a tandem SH2 domain containing tyrosine kinase, have been demonstrated to be associated with the antigen receptor in B cells. Both of these categories of tyrosine kinases are presumed to be critical players in the process of antigen-mediated signal transduction. Cross-linking of membrane immunoglobulin on the surface of B cells leads to the activation of Lyn, Fyn, and Blk, which presumably associate with the cytoplasmic tails of the membrane immunoglobulin-associated Ig alpha/beta heterodimer. Receptor ligation also leads to the tyrosine phosphorylation and catalytic activation of Syk, but the mechanism of association of this kinase with the antigen receptor remains to be established. A number of phosphoproteins that can associate with the SH2 domains of Blk, Lyn, and Fyn have been described in activated B cells. We demonstrate here that Syk is one of the proteins in the lysates of activated B cells which bind to the SH2 domains of Src family kinases. Syk binds directly to the SH2 domain of Blk and complexes in vivo with Lyn and Blk in activated B cells.

Isoflurane and mivacurium chloride neuromuscular blockade in patients with myasthenia gravis

The relaxograph findings are presented in two patients. In the first, isoflurane alone is administered, and mivacurium with isoflurane is administered to the second patient with myasthenia gravis. A significantly lower dose of mivacurium is required. It was noticed that the T4:T1 ratio was 100% after mivacurium and reversal agent, but T1 did not return to normal. In the patient that only received isoflurane, T1 was 60% to 70% of the baseline, indicating the neuromuscular blocking effects of isoflurane. These cases illustrate that inhalation anesthetics are adequate for muscle relaxant effects, and if neuromuscular blockers are necessary, then a lower dose of nondepolarizer should be administered, and the patient carefully monitored. Mivacurium appears to be an ideal agent for neuromuscular blockade in myasthenia gravis as long as careful neuromuscular blockade is performed.

Intraoperative awareness and recall during total hip arthroplasty

A case of intraoperative recall and awareness in a patient with sickle cell disease who had received midazolam, 10 mg at induction of anesthesia, is reported. The patient was on opioids which may also have caused tolerance. Although the use of midazolam may have been judged to provide adequate amnesia, this was clearly not the case. Upon analysis of the reasons for recall, we predicted from a two-compartment model that the estimated blood level was 88 ng/mL-1; this level would have provided no amnesia. This case illustrates that recall can occur with the use of midazolam, especially if levels become subtherapeutic, and other measures should be taken to provide adequate anesthesia and amnesia.

First experimental sutureless end-to-end laser anastomosis of the large bowel. Short-term results

Completely sutureless end-to-end large bowel anastomoses were successfully created in New Zealand white rabbits (n = 26) by using a low-energy (0.4-W wave of power) Nd:YAG laser to produce welded anastomoses. In this study, the short-term integrity, degree of narrowing, macroscopic appearance, and microscopic findings were compared with those of the conventional interrupted one-layer anastomosis (n = 24) at zero, one, four, and seven days after surgery. Two rabbits in the laser group died from leakage. All remaining animals had an uneventful postoperative course. The bursting pressures in the laser group at zero, one, and four days were lower than those in the control group. The narrowing index of the laser anastomosis was higher than that of the suture anastomosis at four and seven days. However, the laser anastomoses showed fewer adhesions, no instances of bowel obstruction, and histologic healing with less fibrosis. The technique of laser anastomosis presents a promising alternative to suturing in reconstitution of the large bowel.

Continuities in sibling relationships: patterns of aggression and friendliness

Thirteen girls and 12 boys who had been observed at home as 2- to 3-year-olds with their mothers and infant siblings were interviewed as 6-year-olds about their relationship with their siblings; their mothers also were interviewed. The marked individual differences found among the 2- to 3-year-olds in comments about their siblings were correlated with differences in the children's comments about their siblings 3-4 years later, and the differences in their behaviour towards their siblings as 2- to 3-year-olds were correlated with differences in their mothers' accounts of the sibling relationship at the 6-year visits.

Bilateral pulmonary agenesis

Two cases of bilateral pulmonary agenesis in infants of 31 and 41 weeks gestation are reported. In addition to absence of both lungs, major abnormalities not previously reported were also found in other systems. It is concluded that these abnormalities are not due to chromosomal abnormality but no alternative can be offered.