Temperature dependent local atomic displacements in NaSn2As2 system

NaSn₂As₂ is mechanically exfoliable layered van der Waals (vdW) Zintl phase that is getting interesting due to its low thermal conductivity and recently observed superconductivity. Here, we have investigated the temperature dependent local structure of NaSn₂As₂ by a combined analysis of As K-edge and Sn K-edge extended x-ray absorption fine structure measurements. The system is intrinsically disordered with the interatomic distances largely consistent to those estimated by average structure measurements. The stretching force constants of different bond distances have been determined using temperature dependent mean square relative displacements. The Sn-As distance is the strongest bond in this system, having covalent nature, unlike the weaker interlayer distances which are characterized by vdW type bonding. Among them, As-Na distance is slightly weaker than Sn-Sn(i) below  ∼200 K and tends to get stronger above this temperature. The anomalous behavior of As-Na bond suggests that the mechanical exfoliation in this system is likely to be temperature dependent. The anomaly in the interlayer atomic correlations may be due to a charge density wave-like instability around this temperature, indicated by earlier experiments. The local structure and disorder are discussed in relation to the physical properties of NaSn₂As₂.

Asymmetric Phosphorus Incorporation in Homoepitaxial P-Doped (111) Diamond Revealed by Photoelectron Holography

Diamond has two crystallographically inequivalent sites in the unit cell. In doped diamond, dopant occupation in the two sites is expected to be equal. Nevertheless, preferential dopant occupation during growth under nonequilibrium conditions is of fundamental importance, for example, to enhance the properties of nitrogen-vacancy (N-V) centers; therefore, this is a promising candidate for a qubit. However, the lack of suitable experimental techniques has made it difficult to study the crystal- and chemical-site-resolved local structures of dopants. Here, we confirm the identity of two chemical sites with asymmetric dopant incorporation in the diamond structure, via the photoelectron holography (PEH) of heavily phosphorus (P)-doped diamond prepared by chemical vapor deposition. One is substitutionally incorporated P with preferential site occupations and the other can be attributed to a PV split vacancy complex with preferential orientation. The present study shows that PEH is a valuable technique to study the local structures around dopants with a resolution of crystallographically inequivalent but energetically equivalent sites/orientations. Such information provides strategies to improve the properties of dopant related-complexes in which alignment is crucial for sensing of magnetic field or quantum spin register using N-V centers in diamond.

An anatomical hypothesis: a "concentric-structured model" for the theoretical understanding of the surgical anatomy in the upper mediastinum required for esophagectomy with radical mediastinal lymph node dissection

Understanding the surgical anatomy is the key to reducing surgical invasiveness especially in the upper mediastinal dissection for esophageal cancer, which is supposed to have a significant impact on curability and morbidity. However, there is no theoretical recognition regarding the surgical anatomy required for esophagectomy, although the surgical anatomy in abdominal digestive surgery has been developed on the basis of embryological findings of intestinal rotation and fusion fascia. Therefore, we developed a hypothesis of a 'concentric-structured model' of the surgical anatomy in the upper mediastinum based on human embryonic development. This model was characterized by three factors: (1) a concentric and symmetric three-layer structure, (2) bilateral vascular distribution, and (3) an 'inter-layer potential space' composed of loose connective tissue. The concentric three-layer structure consists of the 'visceral layer', the 'vascular layer', and the 'parietal layer': the visceral layer containing the esophagus, trachea, and recurrent laryngeal nerves as the central core, the vascular layer of major blood vessels surrounding the visceral core to maintain the circulation, and the parietal layer as the outer frame of the body. The bilateral vascular distribution consists of the inferior thyroid arteries and bronchial arteries originating from the bilateral dorsal aortae in an embryo. This bilateral vascular distribution may be related to the formation of the proper mesentery of the esophagus and frequent lymph node metastasis observed in the visceral layer around recurrent laryngeal nerves. The three concentric layers are bordered by loose connective tissue called the 'inter-layer potential space'. This inter-layer potential space is the fundamental factor of our concentric-structured model as the appropriate surgical plane of dissection. The peripheral blood vessels, nerves, and lymphatics transition between each layer, thereby penetrating this loose connective tissue forming the inter-layer potential space. Recurrent laryngeal nerves also transition from the vascular layer after branching off from the vagal nerves and then ascend consistently in the visceral layer. We investigated the validity of this concentric-structured model, confirming the intraoperative images and the surgical outcomes of thoracoscopic esophagectomy in a prone position (TSEP) before and after the introduction of this hypothetical anatomy model. A total of 226 patients with esophageal cancer underwent TSEP from January 2015 to December 2016. After the introduction of this model, the surgical outcomes in 105 patients clearly improved for the operation time of the thoracoscopic procedure (160 min vs. 182 min, P = 0.01) and the incidence of recurrent laryngeal nerve palsy (19.0% vs. 36.4%, P = 0.004). Moreover, we were able to identify the concentric and symmetric layer structure through surgical dissection along the inter-layer potential space between the visceral and vascular layers ('viscero-vascular space') in all 105 cases after introduction of the hypothetical model. The concentric-structured model based on embryonic development is clinically beneficial for achieving less-invasive esophagectomy by ensuring a theoretical understanding of the surgical anatomy in the upper mediastinum.

Modic changes in the cervical spine: Prospective 20-year follow-up study in asymptomatic subjects

BACKGROUND

Few studies have characterized the development of Modic changes in the cervical spine over time. We evaluated Modic changes of the cervical spine that developed over a 20-year period in a healthy cohort, and sought to clarify the relationship between Modic changes and the development of clinical symptoms.

METHODS

For this multicenter prospective cohort study, we recruited 193 subjects from an original cohort of asymptomatic volunteers who underwent MRI of the cervical spine between 1993 and 1996. Each cervical level from C2/3 to C7/T1 (total n = 1158 intervertebral levels) was assessed on current MRIs as normal or showing type 1, 2, or 3 Modic change, and we asked about symptoms related to the cervical spine. Relationships between the presence of Modic changes and patient characteristics, pre-existing disc degenerations or clinical symptoms were evaluated by logistic regression analysis.

RESULTS

After 20-year follow-up, Modic changes affected 31 subjects (16.1%) at 47 intervertebral disc levels. Of these 47 intervertebral disc levels, type 2, found at 30 levels (63.8%), was the most frequent, followed by type 1 at 15 levels (31.9%) and type 3 at two levels (4.3%). The most frequent changes were observed at the C5/6 segment with type 2 Modic changes. The presence of Modic changes correlated with pre-existing posterior disc protrusion (odds ratio 3.31, 95% confidence interval 1.21-9.05) and neck pain (odds ratio 2.71, 95% confidence interval 1.08-6.80).

CONCLUSIONS

In the cervical spine over a 20-year period, type 2 Modic changes were most frequent at the C5/6 segment. The Modic changes were associated with pre-existing disc degeneration and neck pain but not with age, BMI, smoking, shoulder stiffness, arm pain or numbness.

A 20-year prospective longitudinal MRI study on cervical spine after whiplash injury: Follow-up of a cross-sectional study

BACKGROUND

Some patients suffer from long-lasting symptoms after whiplash injury. However, there are few reports on the long-term changes in the cervical spine after whiplash injury using imaging tests. The purpose of this longitudinal study was to determine the changes on MRI of the cervical spine 20 years after whiplash injury, and to examine the relationships between changes in the cervical spine on MRI and changes in related clinical symptoms.

METHODS

Eighty-one subjects finally participated in this study (follow-up rate 16%). The mean follow-up duration was 21.7 years. All subjects filled out a questionnaire about their clinical symptoms. The MRI findings were assessed using numerical grading system applied in the original study. Statistic analyses were used to investigate whether the progression of each MRI finding was associated with the severity of neck pain, stiff shoulders, dizziness and tinnitus.

RESULTS

All subjects had complained of some clinical symptoms in the original study: 71 had neck pain, 53 stiff shoulders, and others. In the present study, 66 subjects (81.5%) complained of some clinical symptoms: 57 had stiff shoulders, 20 neck pain, and others. The progression of degeneration on MRI was observed in 95% of the subjects, with C4/5 and 5/6 being the most frequently involved levels. Changes in the severity of neck pain, stiff shoulders, dizziness and tinnitus over 20 years were not significantly associated with the progression of degenerative changes in the cervical spine on MRI.

CONCLUSIONS

Twenty years after whiplash injury, 95% of the subjects showed a progression of degeneration in the cervical spine. The progression of the intervertebral disc degeneration in the cervical spine on MRI after whiplash injury was not significantly associated with changes in the severity of related clinical symptoms, indicating that the degenerative changes on MRI may reflect the physiological aging process rather than post-traumatic sequelae.

Prepatterning of Papilio xuthus caterpillar camouflage is controlled by three homeobox genes: clawless, abdominal-A, and Abdominal-B

Color patterns often function as camouflage to protect insects from predators. In most swallowtail butterflies, younger larvae mimic bird droppings but change their pattern to mimic their host plants during their final molt. This pattern change is determined during the early fourth instar by juvenile hormone (JH-sensitive period), but it remains unclear how the prepatterning process is controlled. Using Papilio xuthus larvae, we performed transcriptome comparisons to identify three camouflage pattern-associated homeobox genes [clawless, abdominal-A, and Abdominal-B (Abd-B)] that are up-regulated during the JH-sensitive period in a region-specific manner. Electroporation-mediated knockdown of each gene at the third instar caused loss or change of original fifth instar patterns, but not the fourth instar mimetic pattern, and knockdown of Abd-B after the JH-sensitive period had no effect on fifth instar patterns. These results indicate the role of these genes during the JH-sensitive period and in the control of the prepatterning gene network.

Bridging vein and tentorial sinus in the subtemporal corridor during the anterior transpetrosal approach

BACKGROUND

The bridging vein (BV) and the tentorial sinus (TenS) are important venous structures in neurological surgery. These venous structures during the anterior transpetrosal approach (ATPA) have not been reported. The objective of this study is to examine the BV and the TenS in the subtemporal corridor during the ATPA and propose a technique to identify the BV preoperatively.

METHODS

This study included 126 patients treated via the ATPA. The BV and the TenS located in the operative fields were analyzed. Furthermore, in the preoperative evaluation, the cross-sectional shapes of the intradural vein and the interdural sinus were analyzed by curved planar reconstruction (CPR), and the flattening rate was calculated. Flattening rate = (a-b)/a = 1-b/a (a: long radius, b: short radius).

RESULTS

Seventeen BVs and 18 TenS were identified. The bridging site was divided into two groups: tentorial and middle fossa. The middle fossa group was divided into three subgroups: cavernous sinus, middle fossa dural sinus, and middle fossa dural adherence. Five isolated TenS were sacrificed and no venous complications were observed. The mean flattening rate was 0.13 in the intradural vein and 0.51 in the interdural sinus, respectively (P = 0.0003).

CONCLUSIONS

We showed classification of the BV, and preservation of the BV and TenS during the ATPA. Furthermore, we found that the interdural sinus was significantly flatter than the intradural veins. Measuring the flattening rate by CPR may be useful to identify BVs preoperatively.

Origins of Thermal Spin Depolarization in Half-Metallic Ferromagnet CrO_{2}

Using high-resolution spin-resolved photoemission spectroscopy, we observe a thermal spin depolarization to which all spin-polarized electrons contribute. Furthermore, we observe a distinct minority spin state near the Fermi level and a corresponding depolarization that seldom contributes to demagnetization. The origin of this depolarization has been identified as the many-body effect characteristic of half-metallic ferromagnets. Our investigation opens an experimental field of itinerant ferromagnetic physics focusing on phenomena with sub-meV energy scale.

A 20-Year Prospective Longitudinal Study of Degeneration of the Cervical Spine in a Volunteer Cohort Assessed Using MRI: Follow-up of a Cross-Sectional Study

BACKGROUND

Few studies have addressed in detail long-term degenerative changes in the cervical spine. In this study, we evaluated the progression of degenerative changes of the cervical spine that occurred over a 20-year period in an originally healthy cohort. We also sought to clarify the relationship between the progression of cervical degenerative changes and the development of clinical symptoms.

METHODS

For this prospective follow-up investigation, we recruited 193 subjects from an original cohort of 497 participants who had undergone magnetic resonance imaging (MRI) of the cervical spine between 1993 and 1996. The subjects were asked about the presence or absence of cervical spine-related symptoms. Degenerative changes of the cervical spine were assessed on MRI using an original numerical grading system. The relationship between the progression of degenerative changes and the onset of clinical symptoms was evaluated by logistic regression analysis.

RESULTS

Degeneration in the cervical spine was found to have progressed in 95% of the subjects during the 20-year period. The finding of a decrease in signal intensity of the intervertebral disc progressed in a relatively high proportion of the subjects in all age groups and occurred with similar frequency (around 60%) at all intervertebral disc levels. The rate of progression of other structural failures on MRI increased with age and was highest at C5-C6. The progression of foraminal stenosis was associated with the onset of upper-limb pain (odds ratio, 4.71 [95% confidence interval, 1.02 to 21.7]).

CONCLUSIONS

A progression of degenerative changes in the cervical spine on MRI over the 20-year period was detected in nearly all subjects. There was no relationship between the progression of degeneration on MRI and the development of clinical symptoms, with the exception of an association found between foraminal stenosis and upper-limb pain.

LEVEL OF EVIDENCE

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Imaging scoring systems for preoperative molecular diagnoses of lower-grade gliomas

Recent advance in molecular characterization of gliomas showed that patient prognosis and/or tumor chemosensitivity correlate with certain molecular signatures; however, this information is available only after tumor resection. If molecular information is available by routine radiological examinations, surgical strategy as well as overall treatment strategy could be designed preoperatively.With the aim to establish an imaging scoring system for preoperative diagnosis of molecular status in lower-grade gliomas (WHO grade 2 or 3, LrGGs), we investigated 8 imaging features available on routine CT and MRI in 45 LGGs (discovery cohort) and compared them with the status of 1p/19q codeletion, IDH mutations, and MGMT promoter methylation. The scoring systems were established based on the imaging features significantly associated with each molecular signature, and were tested in the another 52 LrGGs (validation cohort).For prediction of 1p/19q codeletion, the scoring system is composed of calcification, indistinct tumor border on T1, paramagnetic susceptibility effect on T1, and cystic component on FLAIR. For prediction of MGMT promoter methylation, the scoring system is composed of indistinct tumor border, surface localization (FLAIR), and cystic component. The scoring system for prediction of IDH status was not established. The 1p/19q score ≥ 3 showed PPV of 96.2% and specificity of 98.1%, and the MGMT methylation score ≥ 2 showed PPV of 77.4% and specificity of 67.6% in the entire cohort.These scoring systems based on widely available imaging information may help to preoperatively design personalized treatment in patients with LrGG.

The analysis of the cerebral venous blood volume in cavernous sinus using 320 row multi-detector CT

OBJECTIVES

Functional venous anatomy in the brain has been mostly understood from the morphological and embryological points of view and no published study has directly evaluated the blood flow volume of cerebral small veins. We developed a method to directly evaluate the relative blood volume in small venous channels using multi-detector computed tomography (CT) and applied it to evaluate the blood volume in each tributary of the cavernous sinus, which plays an important role in cerebral venous drainage.

PATIENTS AND METHODS

Ten patients with small brain tumors who had normal venous anatomy were included in the present study. All of them underwent preoperative 320-row multi-detector CT. After injecting the contrast bolus, we measured the Hounsfield units (HUs) at 10 time point over 60 s in each tributary of the cavernous sinus. The gamma distribution fitting to each HU enabled us to obtain a time-density curve and determine the relative venous volume in each venous channel.

RESULTS

In terms of blood volume, the superficial middle cerebral vein and inferior petrosal sinus were the largest inflow and outflow channels of the cavernous sinus and accounted for 36.1% and 24.7% of its inflow and outflow on average, respectively. The superior orbital vein did not contribute to the blood volume passing through the cavernous sinus in the current study.

CONCLUSIONS

The present study allowed us to determine the relative blood volume in each tributary of the cavernous sinus, which was very useful to understand the physiological actual venous drainage pattern concerning the cavernous sinus in normal anatomy.

Intraosseous venous structures adjacent to the jugular tubercle associated with an anterior condylar dural arteriovenous fistula

PURPOSE

Although involvement of the osseous component with an anterior condylar dural arteriovenous fistula (AC-DAVF) has been frequently described, osseous venous structures in which AC-DAVFs develop have not been fully elucidated. We investigated osseous venous structures adjacent to the hypoglossal canal in normal controls and patients with AC-DAVFs.

METHODS

The study included 50 individuals with unruptured aneurysms as normal controls and seven patients with AC-DAVFs. Osseous venous structures adjacent to the hypoglossal canal in normal controls were analyzed using computed tomography (CT) digital subtraction venography. In patients with AC-DAVFs, the fistulous pouches, draining veins, and surrounding venous structures were examined using cone beam CT.

RESULTS

In 46.0% of laterals in normal controls, osseous venous structures were visualized within the jugular tubercle superomedially to the hypoglossal canal. We named these structures the jugular tubercle venous complex (JTVC). The JTVC was always continuous with the anterior condylar vein and was sometimes connected to surrounding venous channels. We detected nine fistulous pouches in the seven patients with AC-DAVFs. The fistulous pouches were in the JTVC (33.3%), anterior condylar vein (33.3%), and other venous channels within the exoccipital region (33.3%).

CONCLUSION

Although the JTVC is a venous structure frequently found in normal people, it had not been investigated until now. The venous channel between the anterior condylar vein and JTVC is a common origin site for AC-DAVFs, and it was associated with 66.6% of the AC-DAVF cases in the current study.

Perioperative outcomes of single-port mediastinoscope-assisted transhiatal esophagectomy for thoracic esophageal cancer

We developed an en bloc lymphadenectomy method in the upper mediastinum with a single-port mediastinoscopic cervical approach. This study was designed to evaluate the safety and efficacy of single-port mediastinoscope-assisted transhiatal esophagectomy for thoracic esophageal cancer. The perioperative outcomes of 60 patients with thoracic esophageal cancer who underwent this operation between March 2014 and June 2016 were retrospectively analyzed. The upper mediastinal dissection including lymphadenectomy along the left recurrent laryngeal nerve, using a left cervical approach, was performed with a single-port mediastinoscopic technique, which was used to improve the visibility and handling in the deep mediastinum around the aortic arch. The lymphadenectomy along the right recurrent laryngeal nerve was performed under direct vision using a right cervical approach. Bilateral cervical approaches were followed by hand-assisted laparoscopic transhiatal esophagectomy with en bloc lymphadenectomy in the middle and lower mediastinum. Tumors were mainly located in the middle thoracic esophagus (n = 33), and most tumors were squamous cell carcinoma (n = 58). Pretreatment diagnoses were stage I, 19; II, 13; III, 24; IV, 4. Preoperative chemotherapy was performed for 40 patients. The median operation time and blood loss were 363 minutes and 235 mL, respectively. There were two patients who underwent conversion to thoracotomy. Perioperative complications were evaluated and graded according to the Clavien-Dindo (CD) and the Esophagectomy Complications Consensus Group (ECCG) classifications. Postoperatively, pneumonia was observed in four patients (CD, Grade II, 2; Grade IIIb, 2), although vocal cord palsy was more frequent (ECCG, Type I, 12; Type III, 8). The median number of thoracic lymph nodes resected was 21, and the R0 resection rate was 95%. Single-port mediastinoscope-assisted transhiatal esophagectomy is feasible, in terms of perioperative outcomes, for a radical surgery for thoracic esophageal cancer, although its safety needs to be further demonstrated.

The 67P/Churyumov-Gerasimenko observation campaign in support of the Rosetta mission

We present a summary of the campaign of remote observations that supported the European Space Agency's Rosetta mission. Telescopes across the globe (and in space) followed comet 67P/Churyumov-Gerasimenko from before Rosetta's arrival until nearly the end of the mission in September 2016. These provided essential data for mission planning, large-scale context information for the coma and tails beyond the spacecraft and a way to directly compare 67P with other comets. The observations revealed 67P to be a relatively 'well-behaved' comet, typical of Jupiter family comets and with activity patterns that repeat from orbit to orbit. Comparison between this large collection of telescopic observations and the in situ results from Rosetta will allow us to better understand comet coma chemistry and structure. This work is just beginning as the mission ends-in this paper, we present a summary of the ground-based observations and early results, and point to many questions that will be addressed in future studies.This article is part of the themed issue 'Cometary science after Rosetta'.