Carrier-Density Control of the Quantum-Confined 1T-TiSe_{2} Charge Density Wave.

Using angle-resolved photoemission spectroscopy, combined with first principle and coupled self-consistent Poisson-Schrödinger calculations, we demonstrate that potassium (K) atoms adsorbed on the low-temperature phase of 1T-TiSe_{2} induce the creation of a two-dimensional electron gas (2DEG) and quantum confinement of its charge-density wave (CDW) at the surface. By further changing the K coverage, we tune the carrier density within the 2DEG that allows us to nullify, at the surface, the electronic energy gain due to exciton condensation in the CDW phase while preserving a long-range structural order. Our Letter constitutes a prime example of a controlled exciton-related many-body quantum state in reduced dimensionality by alkali-metal dosing.

Insight into the Charge Density Wave Gap from Contrast Inversion in Topographic STM Images.

Charge density waves (CDWs) are understood in great detail in one dimension, but they remain largely enigmatic in two-dimensional systems. In particular, numerous aspects of the associated energy gap and the formation mechanism are not fully understood. Two long-standing riddles are the amplitude and position of the CDW gap with respect to the Fermi level (E_{F}) and the frequent absence of CDW contrast inversion (CI) between opposite bias scanning tunneling microscopy (STM) images. Here, we find compelling evidence that these two issues are intimately related. Combining density functional theory and STM to analyze the CDW pattern and modulation amplitude in 1T-TiSe_{2}, we find that CI takes place at an unexpected negative sample bias because the CDW gap opens away from E_{F}, deep inside the valence band. This bias becomes increasingly negative as the CDW gap shifts to higher binding energy with electron doping. This study shows the importance of CI in STM images to identify periodic modulations with a CDW and to gain valuable insight into the CDW gap, whose measurement is notoriously controversial.

Bulk and Surface Electronic Structure of the Dual-Topology Semimetal Pt_{2}HgSe_{3}.

We report high-resolution angle-resolved photoemission measurements on single crystals of Pt_{2}HgSe_{3} grown by high-pressure synthesis. Our data reveal a gapped Dirac nodal line whose (001) projection separates the surface Brillouin zone in topological and trivial areas. In the nontrivial k-space range, we find surface states with multiple saddle points in the dispersion, resulting in two van Hove singularities in the surface density of states. Based on density-functional theory calculations, we identify these surface states as signatures of a topological crystalline state, which coexists with a weak topological phase.

Local Real-Space View of the Achiral 1T-TiSe_{2} 2×2×2 Charge Density Wave.

The transition metal dichalcogenide 1T-TiSe_{2}-two-dimensional layered material undergoing a commensurate 2×2×2 charge density wave (CDW) transition with a weak periodic lattice distortion (PLD) below ≈200 K. Scanning tunneling microscopy (STM) combined with intentionally introduced interstitial Ti atoms allows us to go beyond the usual spatial resolution of STM and to intimately probe the three-dimensional character of the PLD. Furthermore, the inversion-symmetric achiral nature of the CDW in the z direction is revealed, contradicting the claimed existence of helical CDW stacking and associated chiral order. This study paves the way to a simultaneous real-space probing of both charge and structural reconstructions in CDW compounds.

Stripe and Short Range Order in the Charge Density Wave of 1T-Cu_{x}TiSe_{2}.

We study the impact of Cu intercalation on the charge density wave (CDW) in 1T-Cu_{x}TiSe_{2} by scanning tunneling microscopy and spectroscopy. Cu atoms, identified through density functional theory modeling, are found to intercalate randomly on the octahedral site in the van der Waals gap and to dope delocalized electrons near the Fermi level. While the CDW modulation period does not depend on Cu content, we observe the formation of charge stripe domains at low Cu content (x<0.02) and a breaking up of the commensurate order into 2×2 domains at higher Cu content. The latter shrink with increasing Cu concentration and tend to be phase shifted. These findings invalidate a proposed excitonic pairing as the primary CDW formation mechanism in this material.

A new approach to the use of α-fetoprotein as surveillance test for hepatocellular carcinoma in patients with cirrhosis.

BACKGROUND: Surveillance for hepatocellular carcinoma (HCC) is recommended in patients with cirrhosis. As α-fetoprotein (AFP) is considered a poor surveillance test, we tested the performance of its changes over time. METHODS: Eighty patients were diagnosed with HCC (cases) during semiannual surveillance with ultrasonography and AFP measurement were recruited and matched for age, gender, etiology and Child-Pugh class with 160 contemporary cancer-free controls undergoing the same surveillance training group (TG). As a validation group (VG) we considered 36 subsequent patients diagnosed with HCC, matched 1 : 3 with contemporary cancer-free controls. α-Fetoprotein values at the time of HCC diagnosis (T0) and its changes over the 12 (Δ12) and 6 months (Δ6) before cancer detection were considered. RESULTS: In both TG and VG, >80% of HCCs were found at an early stage. In TG, AFP significantly increased over time only in cases. T0 AFP and a positive Δ6 were independently associated with HCC diagnosis (odds ratio: 1.031 and 2.402, respectively). The area under the curve of T0 AFP was 0.76 and its best cutoff (BC) was 10 ng ml(-1) (sensitivity 66.3%, specificity 80.6%). The combination of AFP >10 ng ml(-1) or a positive Δ6 composite α-fetoprotein index (CAI) increased the sensitivity to 80% with a negative predictive value (NPV) of 86.2%. Negative predictive value rose to 99%, considering a cancer prevalence of 3%. In the VG, the AFP-BC was again 10 ng ml(-1) (sensitivity 66.7%, specificity 88.9%), and CAI sensitivity was 80.6% with a NPV value of 90.5%. CONCLUSIONS: CAI achieves adequate sensitivity and NPV as a surveillance test for the early detection of HCC in cirrhosis.

Infrared- and Raman-spectroscopy measurements of a transition in the crystal structure and a closing of the energy gap of BiTeI under pressure.

BiTeI is a giant Rashba spin splitting system, in which a noncentrosymmetric topological phase has recently been suggested to appear under high pressure. We investigated the optical properties of this compound, reflectivity and transmission, under pressures up to 15 GPa. The gap feature in the optical conductivity vanishes above p∼9 GPa and does not reappear up to at least 15 GPa. The plasma edge, associated with intrinsically doped charge carriers, is smeared out through a phase transition at 9 GPa. Using high-pressure Raman spectroscopy, we follow the vibrational modes of BiTeI, providing additional clear evidence that the transition at 9 GPa involves a change of crystal structure. This change of crystal structure possibly inhibits the high-pressure topological phase from occurring.

Nature of the bad metallic behavior of Fe1.06Te inferred from its evolution in the magnetic state.

We investigate with angle-resolved photoelectron spectroscopy the changes of the Fermi surface and the main bands from the paramagnetic state to the antiferromagnetic (AFM) state occurring below 72 K in Fe1.06Te. The evolution is completely different from that observed in Fe pnictides, as nesting is absent. The AFM state is a rather good metal, in agreement with our magnetic band structure calculation. On the other hand, the paramagnetic state is very anomalous with a large pseudogap of ~65 meV on the electron pocket that closes in the AFM state. We discuss this behavior in connection with spin fluctuations existing above the magnetic transition and the correlations predicted in the spin-freezing regime of the incoherent metallic state.

Analysis of the risk of a secondary displacement in conservati- vely treated paediatric distal radius metaphyseal fractures. A multicentric study.

OBJECTIVES: Distal radius fractures represent one of the most fre-quent injuries in children. The treatment of choice is a closed reduction followed by immobilisation in plaster cast; the immediate recourse to osteosynthesis with Kirschner wires is only reserved for certain cases. The displacement rate reported in the literature is 21-39%. The aim of this study is to retrospectively evaluate the risk factors for a secondary displacement of metaphyseal radius fractures in a paediatric population treated in three different centres. MATERIALS AND METHODS: The initial treatment for all 360 patients examined was a closed reduction under general anaesthesia and im-mobilisation in an above elbow cast for 4 weeks. The pre-operative displacement, residual post-reduction displacement and possible di-splacement at 7 and 14 days of follow-up were all assessed clinically and radiographically. RESULTS: A loss of reduction was reported in 102 cases; 51 under-went an additional reduction procedure - some followed by osteo-synthesis - while in the remaining 51 cases, the loss of reduction was acceptable in relation to the expectation of remodelling. The most statistically significant variable for the occurrence of a secondary displacement is a severe primary displacement. The association with the ulna fracture is not significantly correlated. The quality of the plaster cast is important for maintaining the reduction. There are a few things to consider as indicators for a second procedure: age, time elapsed from moment of fracture, fracture site and the absence of an acceptable reduction. CONCLUSIONS: In our experience, a reduction followed by osteo-synthesis with Kirschner wires should be considered the treatment of choice in fractures with a high risk of secondary displacement, namely those with severe initial displacement or unsatisfactory reduction.

Epidemiology of thrombocytopenia in patients with chronic hepatitis C: more than meets the eye.

Thrombocytopenia is likely the most common haematological abnormality that can be diagnosed inpatients affected by chronic liver disease. In these patients,the presence of thrombocytopenia may have significant clinical implications. In fact, it can be a limiting factor when considering invasive procedures and may hamper the out come of antiviral therapy with interferon. The prevalence of decreased platelet count in patients with chronic hepatitis Chas been assessed in various studies that evaluated heterogenous patient populations and used various platelet count threshold to identify thrombocytopenia. This review shows that the prevalence of thrombocytopenia in these patients is variable and mainly depends upon the severity of the underlying liver disease and the criterion used to identify this haematological abnormality. Furthermore, the results of this epidemiological review provide an indirect evidence that confirms the multiplicity of aetiological factors underlying the pathophysiology of thrombocytopenia in chronic hepatitis C patients. Lastly, this study shows that up to 25% of patients treated with interferon may develop some degree of thrombocytopenia, and this may be associated with decreased sustained virological response rates.

Successful antiviral therapy determines a significant decrease in squamous cell carcinoma antigen-associated (SCCA) variants' serum levels in anti-HCV positive cirrhotic patients.

Aberrant squamous cell carcinoma antigen (SCCA) expression is an early event in hepatocarcinogenesis, and increasing serum levels of SCCA variants IgM immune complexes (SCCA-IgM IC) have been found in cirrhotic patients developing hepatocellular carcinoma (HCC). We longitudinally evaluated a cohort of cirrhotic patients with hepatitis C virus infection (HCV) who underwent pegylated interferon (PEG-IFN) and ribavirin treatment. SCCA-IgM IC levels were assessed in the sera of 33 cirrhotic patients with HCV (21 males, median age 57 years) before, at the end and at 6-month and 1-year follow-up after treatment with PEG-IFN and ribavirin. SCCA-IgM IC serum levels (arbitrary units/mL, AU/mL) were evaluated according to treatment outcome: sustained virological response (SVR) vs nonresponse (NR). Overall, 15 patients obtained a SVR to antiviral therapy (45%). There was no significant difference in baseline SCCA-IgM IC serum levels between SVR and NR patients. When compared to baseline (451.2 AU/mL), SVR patients showed a significant decrease in median SCCA-IgM IC serum levels at the end of treatment (186.8 AU/mL, P = 0.013) and at both 6-month (96.8 AU/mL, P < 0.001) and 1-year follow-up (52.4 AU/mL, P < 0.001), while no significant modification was observed in NR patients. In patients with HCV-related liver cirrhosis, successful antiviral therapy is associated with a dramatic and significant decrease in SCCA-IC serum levels. Because of the pathophysiological correlation between SCCA and liver carcinogenesis, it is hypothesized that in patients with liver cirrhosis, SVR may be accompanied by a decreased proliferative stimulation.

Infrared conductivity of elemental bismuth under pressure: evidence for an avoided Lifshitz-type semimetal-semiconductor transition.

The application of pressure to elemental bismuth reduces its conduction-valence band overlap, and results in a semimetal-semiconductor (SMSC) transition around 25 kbar. This transition is nominally of the topological "Lifshitz" Fermi surface variety, but there are open questions about the role of interactions at low charge densities. Using a novel pressure cell with optical access, we have performed an extensive study of bismuth's infrared conductivity under pressure. In contrast to the expected pure band behavior we find signatures of enhanced interaction effects, including strongly coupled charge-plasmon (plasmaron) features and a plasma frequency that remains finite up to the transition. These effect are inconsistent with a pure Lifshitz bandlike transition. We postulate that interactions play a central role in driving the transition.

High-field superconductivity in C-doped MgB2 bulk samples prepared by a rapid synthesis route.

The upper critical field sets the thermodynamic limit to superconductivity. A big gap is present between the upper-critical-field values measured in MgB2 polycrystalline bulk superconductors and those of thin films, where values as high as ~ 50 T have been achieved at 4.2 K. Filling this gap would unlock the potential of MgB2 for magnet applications. This work presents the results of an extensive experimental campaign on MgB2 bulk samples, which has been guided by a Design of Experiment. We modeled the dependence of the upper critical field on the main synthesis parameters and established a new record (~ 35 T at 4.2 K) preparing C-doped bulk samples by a non-conventional rapid-synthesis route. This value appears to be an upper boundary for the upper critical field in bulk samples. Structural disorder in films seems to act selectively on one of the two bands where superconductivity in MgB2 takes place: this enhances the upper critical field while reducing the critical temperature only by few Kelvins. On the other hand, the critical temperature in bulk samples decreases monotonically when structural disorder increases, and this imposes a limit to the maximum achievable upper critical field.

Predictive value of on-treatment response during full-dose antiviral therapy of patients with hepatitis C virus cirrhosis and portal hypertension.

OBJECTIVE: Therapy with full-dose pegylated interferon (PEG-IFN) and weight-based ribavirin has been evaluated in limited series of patients with hepatitis C virus (HCV) and advanced disease. In this study, we evaluated the efficacy and tolerability of full-dose antiviral therapy in patients with compensated, fully developed cirrhosis, and assessed the predictive value of on-treatment virological response. DESIGN AND SUBJECTS: We studied 85 HCV-positive cirrhotic patients (82 Child-Pugh class A; 41 treatment-naïve) who were treated with PEG-IFN alpha-2(a) (1.5 microg kg(-1)week(-1)) or alpha-2(b) (180 microg week(-1)) and weight-based ribavirin for 24 (genotype 2-3) or 48 (genotype 1-4) weeks. Forty-three patients were genotype 1 (51%), and HCV-RNA was >600,000 IU mL(-1) in 53 patients (62%). Prevalence of portal hypertension and diabetes was 81% and 18% respectively. RESULTS: Sustained virological response (SVR) was obtained in 22 patients (26%). Positive serum HCV-RNA at week 4 and week 12 of therapy predicted nonresponse (NR) in 85% (52/61) and 100% (38/38) of patients, respectively. Treatment was discontinued due to adverse events in 14 patients (16%). Genotype 1-4 (P = 0.02) and HCV-RNA >600,000 IU mL(-1) (P = 0.02) were the baseline parameters significantly associated with lack of SVR, whilst positive serum HCV-RNA at week 12 was the only parameter independently associated with NR (100% negative predictive value). CONCLUSION: Full-dose antiviral therapy with PEG-IFN and ribavirin can be safely carried out even in patients with compensated, fully established cirrhosis and portal hypertension. Selecting patients on the basis of HCV genotype and viral load, and application of on-treatment stopping rule may help rationalize treatment in patients who are unlikely to obtain SVR.

Imaging the essential role of spin fluctuations in high-T(c) superconductivity.

We have used scanning tunneling spectroscopy to investigate short-length electronic correlations in three-layer Bi2Sr2Ca2Cu3O(10+delta) (Bi-2223). We show that the superconducting gap and the energy Omega(dip), defined as the difference between the dip minimum and the gap, are both modulated in space following the lattice superstructure and are locally anticorrelated. Based on fits of our data to a microscopic strong-coupling model, we show that Omega(dip) is an accurate measure of the collective-mode energy in Bi-2223. We conclude that the collective mode responsible for the dip is a local excitation with a doping dependent energy and is most likely the (pi, pi) spin resonance.

Probing magnetism in 2D materials at the nanoscale with single-spin microscopy.

The discovery of ferromagnetism in two-dimensional (2D) van der Waals (vdW) crystals has generated widespread interest. Making further progress in this area requires quantitative knowledge of the magnetic properties of vdW magnets at the nanoscale. We used scanning single-spin magnetometry based on diamond nitrogen-vacancy centers to image the magnetization, localized defects, and magnetic domains of atomically thin crystals of the vdW magnet chromium(III) iodide (CrI3). We determined the magnetization of CrI3 monolayers to be ≈16 Bohr magnetons per square nanometer, with comparable values in samples with odd numbers of layers; however, the magnetization vanishes when the number of layers is even. We also found that structural modifications can induce switching between ferromagnetic and antiferromagnetic interlayer ordering. These results demonstrate the benefit of using single-spin scanning magnetometry to study the magnetism of 2D vdW magnets.

Development of a provisional core set of response measures for clinical trials of systemic sclerosis.

OBJECTIVE: To develop a provisional core set of response measures for clinical trials of systemic sclerosis (SSc). METHODS: The Scleroderma Clinical Trials Consortium (SCTC) conducted a structured, 3-round Delphi exercise to reach consensus on a core set of measures for clinical trials of SSc. Round 1 asked the SCTC investigators to list items in 11 pre-defined domains (skin, musculoskeletal, cardiac, pulmonary, cardio-pulmonary, gastrointestinal, renal, Raynaud phenomenon and digital ulcers, health-related quality of life and function, global health, and biomarkers) for SSc clinical trials. Round 2 asked respondents to rate the importance of the chosen items and was followed by a meeting, during which the Steering Committee discussed the feasibility, reliability, redundancy and validity of the items. Round 3 sought to obtain broader consensus on the core set measures. Members also voted on items that had data on feasibility but lacked data on reliability and validity, but may still be useful research outcome measures for future trials. RESULTS: A total of 50 SCTC investigators participated in round 1, providing 212 unique items for the 11 domains. In all, 46 (92%) participants responded in round 2 and rated 177 items. The ratings of 177 items were reviewed by the Steering Committee and 31 items from the 11 domains were judged to be appropriate for inclusion in a 1-year multi-centre clinical trial. In total, 40 SCTC investigators completed round 3 and ranked 30 of 31 items as acceptable for inclusion in the core set. The Steering Committee also proposed 14 items for a research agenda. CONCLUSION: Using a Delphi exercise, we have developed a provisional core set of measures for assessment of disease activity and severity in clinical trials of SSc.

Hepatocellular carcinoma recurrence in patients with curative resection or ablation: impact of HCV eradication does not depend on the use of interferon.

BACKGROUND: In HCV-infected cirrhotic patients with successfully treated early hepatocellular carcinoma (HCC), the time to HCC recurrence and the effects of sustained viral eradication (SVR) by interferon (IFN)-based or IFN-free regimens on HCC recurrence remain unclear. AIM: To perform an indirect comparison of time to recurrence (TTR) in patients with successfully treated early HCC and active HCV infection with those of patients with SVR by IFN-based and by IFN-free regimens. METHODS: We evaluated 443 patients with HCV-related cirrhosis and Barcelona Clinic Liver Cancer Stage A/0 HCC who had a complete radiological response after curative resection or ablation. Active HCV infection was present in 328, selected from the Italian Liver Cancer group cohort; 58 patients had SVR achieved by IFN-free regimens after HCC cure, and 57 patients had SVR achieved by IFN-based regimens after HCC cure. Individual data of patients in the last two groups were extracted from available publications. RESULTS: TTR by Kaplan-Meier curve was significantly lower in patients with active HCV infection compared with those with SVR both by IFN-free (P = 0.02) and by IFN-based (P < 0.001) treatments. TTR was similar in patients with SVR by IFN-free or by IFN-based (P = 0.49) strategies. CONCLUSION: In HCV-infected, successfully treated patients with early HCC, SVR obtained by IFN-based or IFN-free regimens significantly reduce tumour recurrence without differences related to the anti-viral strategy used.