CO-tip manipulation using repulsive interactions.

Understanding the interactions between a tip apex and a target atom or molecule is crucial for the manipulation of individual molecules with precise control by using scanning tunnelling microscopy (STM) and atomic force microscopy. Herein, we demonstrate the manipulation of target CO molecules on a Cu(111) substrate using a CO-functionalized W tip with atomic-scale accuracy. All experiments were performed in a home-built ultra-high vacuum STM system at 5 K. The CO-tip was fabricated by picking up a single CO molecule from a Cu(111) surface. In contrast to a metal tip, repulsive interactions occur between the CO-tip and the target CO molecule. This repulsive interaction promises perfect lateral hopping without any vertical hopping. Hopping events were directly monitored as sudden current drops in the simultaneously measured I-z curves. A larger barrier height between the CO-tip and the target CO (∼9.5 eV) was found from the slope of the I-z curve, which decreases the electron tunnelling probability between the tip and sample. Therefore, electron-driven manipulation cannot be a major trigger for the CO-CO repulsive manipulation. The CO-tip is able to manipulate only the target CO molecule, even when another CO molecule was located ∼0.5 nm away. Statistical measurements revealed that the nearest neighbour atop site is the energetically stable position after hopping. However, if the CO target has another CO molecule in a neighbouring position (denoted as a 'pair'), the target CO hops more than twice as far. This means that the CO-tip experiences a larger repulsive interaction from the pair. These observations of CO-tip manipulation are useful for the design of two-dimensional artificial molecular networks as well as for developing a better understanding of catalytic oxidation processes.

Electron-bombarded ⟨110⟩-oriented tungsten tips for stable tunneling electron emission.

A clean tungsten (W) tip apex with a robust atomic plane is required for producing a stable tunneling electron emission under strong electric fields. Because a tip apex fabricated from a wire by aqueous chemical etching is covered by impurity layers, heating treatment in ultra-high vacuum is experimentally known to be necessary. However, strong heating frequently melts the tip apex and causes unstable electron emissions. We investigated quantitatively the tip apex and found a useful method to prepare a tip with stable tunneling electron emissions by controlling electron-bombardment heating power. Careful characterizations of the tip structures were performed with combinations of using field emission I-V curves, scanning electron microscopy, X-ray diffraction (transmitted Debye-Scherrer and Laue) with micro-parabola capillary, field ion microscopy, and field emission microscopy. Tips were chemically etched from (1) polycrystalline W wires (grain size ∼1000 nm) and (2) long-time heated W wires (grain size larger than 1 mm). Heating by 10-40 W (10 s) was found to be good enough to remove oxide layers and produced stable electron emission; however, around 60 W (10 s) heating was threshold power to increase the tip radius, typically +10 ± 5 nm (onset of melting). Further, the grain size of ∼1000 nm was necessary to obtain a conical shape tip apex.

Recovery of nanomolecular electronic states from tunneling spectroscopy: LDOS of low-dimensional phthalocyanine molecular structures on Cu(111).

Organic nanomolecules have become one of the most attractive materials for new nanoelectronics devices. Understanding of the electronic density of states around the Fermi energy of low-dimensional molecules is crucial in designing the electronic properties of molecular devices. The low dimensionality of nanomolecules results in new electronic properties owing to their unique symmetry. Scanning tunneling spectroscopy is one of the most effective techniques for studying the electronic states of nanomolecules, particularly near the Fermi energy (±1.5 eV), whereas these molecular electronic states are frequently buried by the tunneling probability background in tunneling spectroscopy, resulting in incorrect determination of the molecular electronic states. Here, we demonstrate how to recover nanomolecular electronic states from dI/dV curves obtained by tunneling spectroscopy. Precise local density of states (LDOS) peaks for low-dimensional nanostructures (monolayer ultrathin films, one-dimensional chains, and single molecules) of phthalocyanine (H2Pc) molecules grown on noble fcc-Cu(111) were obtained.

Magnetoelectric coupling at metal surfaces.

Magnetoelectric coupling allows the magnetic state of a material to be changed by an applied electric field. To date, this phenomenon has mainly been observed in insulating materials such as complex multiferroic oxides. Bulk metallic systems do not exhibit magnetoelectric coupling, because applied electric fields are screened by conduction electrons. We demonstrate strong magnetoelectric coupling at the surface of thin iron films using the electric field from a scanning tunnelling microscope, and are able to write, store and read information to areas with sides of a few nanometres. Our work demonstrates that high-density, non-volatile information storage is possible in metals.

Evaluation of sample spin-polarization from spin-polarized scanning tunneling spectroscopy experiments.

Spin-polarized scanning tunneling microscopy has produced a great amount of images presenting magnetic contrast between different magnetic domains with an unsurpassed spatial resolution but getting values like the surface polarization has proven to be a difficult task. We will discuss in detail how to extract this information for the case of manganese layers grown on Fe(001) whiskers. Mn layers adopt a body-centered-tetragonal (bct) structure when they are grown on the Fe(001) surface at room temperature. The Mn layers show an antiferromagnetic coupling between the layers. Comparing our spin-polarized scanning tunneling spectra measured with Fe-coated W tips with spin-resolved band structure calculations, we are able to find the value of the sample surface polarization. Also discussed is a method to change the tip magnetization. Finally, the magnetic structure around a screw dislocation on the surface is reviewed.

A comprehensive and validated molecular taxonomy of beaked whales, family Ziphiidae.

DNA sequences from orthologous loci can provide universal characters for taxonomic identification. Molecular taxonomy is of particular value for groups in which distinctive morphological features are difficult to observe or compare. To assist in species identification for the little known family Ziphiidae (beaked whales), we compiled a reference database of mitochondrial DNA (mtDNA) control region (437 bp) and cytochrome b (384 bp) sequences for all 21 described species in this group. This mtDNA database is complemented by a nuclear database of actin intron sequences (925 bp) for 17 of the 21 species. All reference sequences were derived from specimens validated by diagnostic skeletal material or other documentation, and included four holotypes. Phylogenetic analyses of mtDNA sequences confirmed the genetic distinctiveness of all beaked whale species currently recognized. Both mitochondrial loci were well suited for species identification, with reference sequences for all known ziphiids forming robust species-specific clades in phylogenetic reconstructions. The majority of species were also distinguished by nuclear alleles. Phylogenetic comparison of sequence data from "test" specimens to these reference databases resulted in three major taxonomic discoveries involving animals previously misclassified from morphology. Based on our experience with this family and the order Cetacea as a whole, we suggest that a molecular taxonomy should consider the following components: comprehensiveness, validation, locus sensitivity, genetic distinctiveness and exclusivity, concordance, and universal accessibility and curation.

Observation of spin-polarized surface states on ultrathin bct Mn(001) films by spin-polarized scanning tunneling spectroscopy.

We report the observation of a magnetic contrast of up to 20% in the scanning tunneling spectroscopy dI/dV maps obtained with Fe-coated tips on Mn(001) layers grown on an Fe(001) whisker at 370 K. These nanometer resolution microscopy results show that the layers couple antiferromagnetically. By normalizing the dI/dV curves by tunneling probability functions, we found a spin-dependent peak on the body-centered-tetragonal (bct) Mn(001) surface at +0.8 V, whose high spin polarization gives rise to the dI/dV map contrast. Band structure calculations allow one to identify the +0.8 V peak as due to two spin-polarized d(z(2)) surface states.

DNA analysis of a grandfather-father-son relationship from 300-year-old remains of the Date clan in Japan.

The grandfather-father-son relationship of the first three lords of the Date clan in Japan was ascertained by HLA-DNA sequencing analysis. From their hairs and dried lung tissue found in ca. 300-year-old remains, DNA was extracted with usual phenol-chloroform method followed by purification with cetyltrimethylammonium bromide (CTAB). Two HLA class II genes, HLA-DQA1 and -DPB1, were amplified by seminested, or dual/triple PCR. The PCR products were cloned and analyzed by automated sequencing. Since the three lords shared a haplotype of DQA1*0301-DPB1*0402, we concluded that there is no inconsistency in their lineage. This is the first case of biological evidence for a historical Samurai family relationship in the 17-18th centuries.

Testicular morphology of a greater Indian rhinoceros (Rhinoceros unicornis).

The testis of a greater Indian rhinoceros (Rhinoceros unicornis) was examined by naked eyes and light microscopy. The animal sampled was estimated to be 42 years old. Testis was ellipse-shaped and weighed 1,300 g. Although a number of elongated spermatids were distinguishable in some seminiferous tubules, the lumen of seminiferous tubules was closed and connective tissues conspicuously increased in amount in the intertubular space. These findings in testicular morphology of the animal may be due to ageing.

Ultrastructure of cardiac myocyte in the Asian elephant (Elephas maximus).

Cardiac myocytes of an Asian elephant (Elephas maximus) were observed by transmission electron microscopy. Typical ultrastructural features of cardiac myocytes are exhibited in the musculature of both the left and right atria, and left ventricle of the heart. Myofibrils, mitochondria, T-system and sarcoplasmic reticulum are well-developed within the cytoplasm. Many mitochondria are characteristically concentrated is some myocytes. Cardiac musculature is also distributed in the root of the caudal vena cava. Many atrial granules are detected not only in atrial myocytes, but also in the myocytes of the caudal vena cava. Atrial natriuretic polypeptide may be secreted from the caval venous wall in the elephant.

Nerve supply to the accessory soleus muscle.

An accessory soleus muscle was found in the right leg of a cadaver in the dissecting room. This anomalous muscle was situated medially between the distal part of the tibia and the tendo calcaneus. The muscle arose from the anterior aponeurosis of the soleus muscle and was attached with a separate tendon to the calcaneus anteromedial to the tendo calcaneus. The soleus muscle was supplied by two nerves from the tibial nerve. The ramus posterior entered its posterior surface near the proximal border, and the ramus anterior entered the bipenniform part which was located on the anterior aspect of the soleus. One of branches from the r. anterior descended on the surface of the medial half of the bipenniform part and gave off a few twigs for this muscle part. Finally, its terminal entered the accessory soleus muscle and ramified in this muscle. In a teased preparation of the tibial nerve, both the nerve fibres composing this branch to the anomalous muscle and those constituting the r. anterior proper which supplied the bipenniform part were contained in the same funiculus. This mode of nerve supply to the soleus and the accessory soleus muscle suggested that this anomalous muscle derived from the part of the proper soleus muscle supplied by the r. anterior.

Classification of the abdominal splanchnic nerves--a preliminary attempt to re-evaluate their nomenclatures.

The abdominal splanchnic nerves were observed in 22 cadavers (41 sides). The purpose of the study is to give more accurate definition to each nerve, for there are uncertainties in the nomenclature of these nerves. According to PNA, the abdominal splanchnic nerves are classified into three categories, on the basis of their sizes and their levels, namely Nn. splanchnici major, minor, and imus. Although Mitchell (1935) had already claimed that more attention should be given to the levels of ganglia which gave rise to these nerves, no revision has ever been made. Moreover, there still remains the matter of their destinations, which are more significant in defining them. Therefore, in addition to the conventional criteria for the classification, destinations of the nerves were taken into consideration. In the present study, 36 out of 41 sides were grouped into four types according to the said criteria. 5 exceptional cases were interpreted as results of minor modifications of these four types. Naturally, what is important in describing these nerves is to give clear idea about the actual condition of them. It is expected to give more reasonable nomenclature to these nerves based on the present result.

A new classification of the brachial extensors in Tarsius.

The muscular system of the tarsier was first described by Burmeister (1846), who noted that brachial extensors (triceps complex) have six heads. The first three heads, respectively, correspond to the long, lateral and medial heads of the triceps brachii muscle in man. The fourth head is the anconaeus and the fifth is the dorsoepitrochlearis. Schultz (1984) divided the sixth head into two different parts (preaxial and postaxial) from the viewpoint of nerve supply. The present study found that the whole sixth head is innervated by the ulnar nerve, and we propose that it is recognized as the proximal and distal heads of the (preaxial) epitrochleoanconaeus muscle. The proximal head may have developed specially in the tarsier in addition to the distal head observed in other prosimians. It is thought to support the extension of the elbow joint and contribute to the tarsier's effective locomotion.

Aberrant cutaneous nerve of the thigh arising from the sciatic nerve in the human.

An aberrant cutaneous nerve of the thigh arising from the peroneal portion of the human sciatic nerve or common peroneal nerve was observed in 9 cases (4.6% of sides). After giving a branch to the short head of the biceps femoris muscle and a branch to the knee joint, this cutaneous nerve reaches the subcutaneous tissue by passing between the short head of the biceps femoris and the vastus lateralis or by piercing through the biceps femoris. The authors presume that the cutaneous nerve shows the presence of the potential cutaneous nerve routes from the common peroneal nerve to the skin of the lateral aspect of the thigh.