The Processing Behavior of Liquid Sn/Molten Polyethylene during Internal Mixing

In our study, liquid tin (Sn) was mixed with molten polyethylene using an internal mixer; the interfacial tension between the liquid Sn and molten polyethylene was measured using the deformed drop retraction method. The results showed that liquid Sn separated when the Sn content was higher than approximately 2 % by volume because of the interfacial tension of up to 167 mN/m and the 106-fold viscosity difference between the liquid Sn and the molten polyethylene. When Sn separation did not occur, the effects of the mixing time and rotary speed on the degree of mixing and the Sn particle size were analyzed using thermogravimetric analysis and scanning electron microscopy. The results showed that the effects of mixing time and rotary speed on the degree of mixing and Sn particle size can be combined as the impact of specific energy input. With increasing specific energy input, the degree of mixing initially increased and subsequently remained constant, while the Sn particle size initially decreased and subsequently remained constant. The refinement of the dispersed phase was completed with a low specific energy input, but the homogenization of the dispersed phase required a higher specific energy input to achieve completion, revealing the relationship between distributive mixing and dispersive mixing.

VNP: Interactive Visual Network Pharmacology of Diseases, Targets, and Drugs

In drug discovery, promiscuous targets, multifactorial diseases, and "dirty" drugs construct complex network relationships. Network pharmacology description and analysis not only give a systems-level understanding of drug action and disease complexity but can also help to improve the efficiency of target selection and drug design. Visual network pharmacology (VNP) is developed to visualize network pharmacology of targets, diseases, and drugs with a graph network by using disease, target or drug names, chemical structures, or protein sequence. To our knowledge, VNP is the first free interactive VNP server that should be very helpful for systems pharmacology research. VNP is freely available at http://cadd.whu.edu.cn/ditad/vnpsearch.

Downregulation of the tumor suppressor HSPB7, involved in the p53 pathway, in renal cell carcinoma by hypermethylation

In order to identify genes involved in renal carcinogenesis, we analyzed the expression profile of renal cell carcinomas (RCCs) using microarrays consisting of 27,648 cDNA or ESTs, and found a small heat shock protein, HSPB7, to be significantly and commonly downregulated in RCC. Subsequent quantitative PCR (qPCR) and immunohistochemical (IHC) analyses confirmed the downregulation of HSPB7 in RCC tissues and cancer cell lines in both transcriptional and protein levels. Bisulfite sequencing of a genomic region of HSPB7 detected DNA hypermethylation of some segments of HSPB7 in RCC cells and concordantly 5-aza-2'-deoxycytidine (5-Aza-dC) treatment of cancer cells restored HSPB7 expression significantly. Ectopic introduction of HSPB7 in five RCC cell lines remarkably suppressed cancer cell growth. Interestingly, we found that HSPB7 expression could be induced by p53 in a dose-dependent manner, indicating that this gene functions in the p53 pathway. Our results imply that HSBP7 is likely to be a tumor suppressor gene regulated by p53 and its downregulation by hypermethylation may play a critical role in renal carcinogenesis.

Anatomical research on the subacromial interval following implantation of clavicle hook plates

This article aimed to explore whether hook plate implantation significantly narrowed the subacromial space. 24 shoulder joints were implanted with clavicle hook plates. A Vernier caliper was used to measure the length and thickness of the acromion. In addition, the length and thickness of the hook of the plate were measured. The data from all measurements recorded were divided into 2 groups Group A, the length group: the length of acromion and the hook, and Group B, the thickness group: the thickness of acromion and the depth of hook. There are significant statistical differences when comparing between the subgroups within each group. The depth of the hook exceeds the thickness of the acromion (12.41±2.80 mm vs. 10.44±2.59 mm, respectively), the hook plate implantation significantly narrowed the subacromial space by 1.97±1.19 mm (p<0.01), and the length of the hook was shorter than that of the acromion by 9.75±3.64 mm (p<0.01). Our findings revealed that the hook plate with only 3 depths could not match the acromion satisfactorily and the hook plate implantation significantly narrowed the subacromial space. A hook plate with a variable depth, which can match better with patient's anatomy, is worthy of further investigation in the future.

Characterization of the novel HLA-DPA1*02:05 allele identified by sequence-based typing

The novel HLA-DPA1*02:05 variant allele differs from the closest allele DPA1*02:02:02.

Reduction of osteopontin in vivo inhibits tubular epithelial to mesenchymal transition in rats with chronic allograft nephropathy

OBJECTIVE

Chronic allograft nephropathy (CAN) is an important etiological factor causing graft loss. However, the mechanism of CAN is unclear. Osteopontin (OPN), a proinflammatory and profibrosis molecule, plays a key role in late stages of renal diseases. We investigated the potential role of OPN in the pathogenesis of CAN.

METHODS

Using a F344 to Lewis rat CAN model, we injected short hairpin RNA (shRNA) constructs targeting OPN or negative control plasmids through the renal vein following electroporation. At 12 weeks after the transplantation, we determined interstitial fibrosis (IF) and tubular atrophy (TA) of the tubular epithelial cells (TECs). OPN expression was examined using Western blots and immunohistochemistry (IHC). Molecules involved in epithelial to mesenchymal transition (EMT) of TECs were examined using IHC and Western blots.

RESULTS

OPN expression in kidney grafts was decreased by the RNA interference (RNAi) group. Histology observations showed IF and TA to be mild with stable renal function in the RNAi-treated group. EMT of TECs was significantly lessened after reducing OPN.

CONCLUSION

Reduction of OPN in vivo inhibited progression of CAN. OPN may be of therapeutic value in transplantation settings.

Scaphoid nonunion reconstructed with vascularized bone-grafting pedicled on 1,2 intercompartmental supraretinacular artery and external fixation

BACKGROUND

Vascularized bone-grafting pedicled on 1,2 intercompartmental supraretinacular artery (1,2 ICSRA) has been recommended as a treatment alternative for established scaphoid nonunion complicated with proximal pole avascular necrosis (AVN). Previous reports focused the studies on the union rate and the revascularization of the transferred graft. However, the postoperative wrist stiffness still a challenging problem and remaining to be solved. The purpose of our study was to determine whether the combination of vascularized bone-grafting pedicled on 1,2 ICSRA and wrist external fixator immobilization provides a more effective strategy for treating established scaphoid nonunion complicated with AVN and improving postoperative range of motion (ROM) of the injured wrist.

PATIENTS AND METHODS

We retrospectively reviewed a consecutive series of 11 patients who had cases of established scaphoid nonunion involving AVN of the proximal pole were treated with vascularized bone-grafting pedicled on 1,2 1,2 ICSRA, internal fixation, and wrist external fixator immobilization. Procedure of wrist arthrolysis was performed before vascularized bone graft transferring. Preoperative and postoperative evaluation included measurement of clinical (wrist ROM and grip strength), radiographic (intrascaphoid angle, scapholunate angle) and functional (Mayo wrist score) parameters.

RESULTS

Osseous union was achieved in all of the 11 cases within an average period of 11.4 weeks. On an average 6.1 years follow-up, there were three excellent, six good and two fair results. Significant improvements were found for Mayo wrist score, wrist ROM, and grip strength (p < 0.01). Intrascaphoid angle and scapholunate angle were significantly improved postoperatively, and there was no significant difference between the postoperative values and the values at the last follow-up. Early functional rehabilitation of the injured wrist under the protection of the fixator did not result in displacement of the transferred graft.

CONCLUSIONS

The results of the present investigation support the use of the vascularized bone graft pedicled on 1,2 ICSRA in the treatment of scaphoid nonunion complicated with proximal pole AVN. Procedures of wrist arthrolysis and early institution of wrist functional rehabilitation under the protection of the external fixator play important role in the restoration of range of motion of the injured wrist.  

Isolation and characterization of fatty acid methyl ester (FAME)-producing Streptomyces sp. S161 from sheep (Ovis aries) faeces

An actinomycete producing oil-like mixtures was isolated and characterized. The strain was isolated from sheep faeces and identified as Streptomyces sp. S161 based on 16S rRNA gene sequence analysis. The strain showed cellulase and xylanase activities. The (1) H nuclear magnetic resonance (NMR) spectra of the mixtures showed that the mixtures were composed of fatty acid methyl esters (52·5), triglycerides (13·7) and monoglycerides (9·1) (mol.%). Based on the gas chromatography-mass spectrometry (GC-MS) analysis, the fatty acid methyl esters were mainly composed of C14-C16 long-chain fatty acids. The results indicated that Streptomyces sp. S161 could produce fatty acid methyl esters (FAME) directly from starch. To our knowledge, this is the first isolated strain that can produce biodiesel (FAME) directly from starch.

Development and characterization of SCAR markers linked to the citrus tristeza virus resistance gene from Poncirus trifoliata

Twelve new dominant randomly amplified polymorphic DNA (RAPD) fragments associated with a single dominant gene for resistance to citrus tristeza virus (CTV) were identified using bulked segregant analysis of an intergeneric backcross family. These and eight previously reported RAPDs were mapped in the resistance gene (Ctv) region; the resulting localized linkage map spans about 32 cM, with nine close flanking markers within 2.5 cM of Ctv. Seven of 20 RAPD fragments linked with the resistance gene were cloned and sequenced, and their sequences were used to design longer primers to develop sequence characterized amplified region (SCAR) markers that can be utilized reliably in marker-assisted selection, high-resolution mapping, and map-based cloning of the resistance gene. All seven cloned RAPDs were converted successfully into SCARs by redesigning primers, optimizing PCR parameters (especially the annealing temperature), or digesting amplification products with restriction enzymes. Four of the seven remained dominant markers, displaying presence-absence polymorphism patterns; the other three detected restriction site changes or length variations and thus were transformed into codominant markers. Two genomic regions rich in variability were also detected by two codominant SCAR markers.

Soluble MICA and a MICA variation as possible prognostic biomarkers for HBV-induced hepatocellular carcinoma

MHC class I polypeptide-related chain A (MICA) molecule is induced in response to viral infection and various types of stress. We recently reported that a single nucleotide polymorphism (SNP) rs2596542 located in the MICA promoter region was significantly associated with the risk for hepatitis C virus (HCV)-induced hepatocellular carcinoma (HCC) and also with serum levels of soluble MICA (sMICA). In this study, we focused on the possible involvement of MICA in liver carcinogenesis related to hepatitis B virus (HBV) infection and examined correlation between the MICA polymorphism and the serum sMICA levels in HBV-induced HCC patients. The genetic association analysis revealed a nominal association with an SNP rs2596542; a G allele was considered to increase the risk of HBV-induced HCC (P = 0.029 with odds ratio of 1.19). We also found a significant elevation of sMICA in HBV-induced HCC cases. Moreover, a G allele of SNP rs2596542 was significantly associated with increased sMICA levels (P = 0.009). Interestingly, HCC patients with the high serum level of sMICA (>5 pg/ml) exhibited poorer prognosis than those with the low serum level of sMICA (≤5 pg/ml) (P = 0.008). Thus, our results highlight the importance of MICA genetic variations and the significance of sMICA as a predictive biomarker for HBV-induced HCC.

Traumatic forequarter amputation associated acute lung injury (ALI): report of one case

One case of traumatic forequarter amputation associated acute lung injury (ALI) was presented. A discussion reviewing the treatment guidelines for this devastating injury, and pointing out the importance of supporting the lung and preventing the development of acute respiratory distress syndrome (ARDS) was included.

A novel HLA-A allele detected by sequence-based typing: A*11:01:18

HLA-A*11:01:18 shows one nucleotide difference at genomic nt 331 G>A (codon 43 CAG>CAA) in exon 2.

Rapid auxin-mediated changes in the proteome of the epidermal cells in rye coleoptiles: implications for the initiation of growth

In axial organs of juvenile plants, the phytohormone auxin (indole-3-acetic acid, IAA) rapidly mediates cell wall loosening and hence promotes turgor-driven elongation. In this study, we used rye (Secale cereale) coleoptile sections to investigate possible effects of IAA on the proteome of the cells. In a first set of experiments, we document that IAA causes organ elongation via promotion of expansion of the rigid outer wall of the outer epidermis. A quantitative comparison of the proteome (membrane-associated proteins), using two-dimensional difference gel electrophoresis (2-D DIGE), revealed that, within 2 h of auxin treatment, at least 16 protein spots were up- or down-regulated by IAA. These proteins were identified using reverse-phase liquid chromatography electrospray tandem mass spectrometry. Four of these proteins were detected in the growth-controlling outer epidermis and were further analysed. One epidermal polypeptide, a small Ras-related GTP-binding protein, was rapidly down-regulated by IAA (after 0.5 h of incubation) by -35% compared to the control. Concomitantly, a subunit of the 26S proteasome was up-regulated by IAA (+30% within 1 h). In addition, this protein displayed IAA-mediated post-translational modification. The implications of these rapid auxin effects with respect to signal transduction and IAA-mediated secretion of glycoproteins (osmiophilic nano-particles) into the growth-controlling outer epidermal wall are discussed.

Rapid auxin-mediated changes in the proteome of the epidermal cells in rye coleoptiles: implications for the initiation of growth

In axial organs of juvenile plants, the phytohormone auxin (indole-3-acetic acid, IAA) rapidly mediates cell wall loosening and hence promotes turgor-driven elongation. In this study, we used rye (Secale cereale) coleoptile sections to investigate possible effects of IAA on the proteome of the cells. In a first set of experiments, we document that IAA causes organ elongation via promotion of expansion of the rigid outer wall of the outer epidermis. A quantitative comparison of the proteome (membrane-associated proteins), using two-dimensional difference gel electrophoresis (2-D DIGE), revealed that, within 2 h of auxin treatment, at least 16 protein spots were up- or down-regulated by IAA. These proteins were identified using reverse-phase liquid chromatography electrospray tandem mass spectrometry. Four of these proteins were detected in the growth-controlling outer epidermis and were further analysed. One epidermal polypeptide, a small Ras-related GTP-binding protein, was rapidly down-regulated by IAA (after 0.5 h of incubation) by -35% compared to the control. Concomitantly, a subunit of the 26S proteasome was up-regulated by IAA (+30% within 1 h). In addition, this protein displayed IAA-mediated post-translational modification. The implications of these rapid auxin effects with respect to signal transduction and IAA-mediated secretion of glycoproteins (osmiophilic nano-particles) into the growth-controlling outer epidermal wall are discussed.

Characterization of the genomic full-length sequence of C*04:03 and C*04:06 in Chinese Han individuals

The genomic full-length sequences of C*04:03 and C*04:06 were first identified by cloning and sequencing.

Characterization of a novel variant allele, HLA-C*07:01:19, identified in a Chinese Han individual

The novel HLA-C*07:01:19 allele differs from the closest allele C*07:01:01 by a single nucleotide change at coding sequence nucleotide 738 G>A (codon 222 GAG>GAA) in exon 4.

Characterization and polymorphic analysis of 4.5 kb genomic full-length HLA-C in the Chinese Han population

This study used long-range polymerase chain reaction to sequence 4.5 or 4.3 kb of genomic DNA covering human leukocyte antigen C (HLA-C) and its flanks in 45 Chinese Han subjects to better characterize variation in the gene in a single population. Sequences of 35 HLA-C alleles were obtained from the population, including major alleles of 13 lineages of HLA-C. Four novel alleles, C*03:04:01:02, C*04:01:01:03, C*08:22, and C*17:01:01:02, were identified, and complete full-length sequences of 18 HLA-C alleles were obtained for the first time. All sequences herein reported also represent extensions through the promoter region and the 3'-untranslated region. Fourteen 5'-nucleotide sequences and 14 3'-nucleotide sequences were detected outside the coding region. In total, 316 single-nucleotide polymorphisms unequally distributed in HLA-C subregions were observed. In addition to exons 2 and 3, nucleotide variability was found to be particularly high in exon 5, which encodes the transmembrane region. The differentiation of the C*07 and C*17 lineages in this region accounts for the high variability. The congruence of phylogeny across most regions of the gene suggests that gene conversion or recombination has not markedly influenced divergence between lineages in the evolution of HLA-C.

MicroRNA miR-93 promotes tumor growth and angiogenesis by targeting integrin-β8

It has been reported that the miR-106b∼25 cluster, a paralog of the miR-17∼92 cluster, possesses oncogenic activities. However, the precise role of each microRNA (miRNA) in the miR-106b∼25 cluster is not yet known. In this study, we examined the function of miR-93, one of the microRNAs within the miR-106b∼25 cluster, in angiogenesis and tumor formation. We found that miR-93 enhanced cell survival, promoted sphere formation and augmented tumor growth. Most strikingly, when miR-93-overexpressing U87 cells were co-cultured with endothelial cells, they supported endothelial cell spreading, growth, migration and tube formation. In vivo studies revealed that miR-93-expressing cells induced blood vessel formation, allowing blood vessels to extend to tumor tissues in high densities. Angiogenesis promoted by miR-93 in return facilitated cell survival, resulting in enhanced tumor growth. We further showed that integrin-β8 is a target of miR-93. Higher levels of integrin-β8 are associated with cell death in tumor mass and in human glioblastoma. Silencing of integrin-β8 expression using small interfering RNA promoted cell proliferation, whereas ectopic expression of integrin-β8 decreased cell growth. These findings showed that miR-93 promotes tumor growth and angiogenesis by suppressing, at least in part, integrin-β8 expression. Our results suggest that inhibition of miR-93 function may be a feasible approach to suppress angiogenesis and tumor growth.

Superconductivity above 33 K in (Ca(₁ - x)Na(x))Fe₂As₂

We report the synthesis of (Ca₀.₃₃Na₀.₆₆)Fe₂As₂ showing a superconducting transition with T(c) above 33 K. Both dc magnetic susceptibility or specific heat measurements indicated the bulk superconductivity nature of the sample. We also have successfully grown single crystals of the (Ca₀.₃₃Na₀.₆₆)Fe₂As₂ superconductors. The single crystals exhibit sharp superconducting transitions with T(c) above 33 K. The effects of magnetic field on the superconducting transitions are studied, giving rise to high upper critical fields with H(c₂)(c)≈85 T and H(c₂)(ab)≈172 T, respectively. The anisotropy parameter was calculated to be around 2.

Cessation of coleoptile elongation and loss of auxin sensitivity in developing rye seedlings: a quantitative proteomic analysis

The use of the grass coleoptile for the elucidation of the mechanism of cell elongation is a legacy of the classic experiments of Charles Darwin, who described this organ in 1880 as a "reddish sheath". In this study we quantified the growth of intact, etiolated rye (Secale cereale L.) seedlings and selected 3-day-old (growing) vs. 4-day-old (pierced) coleoptiles for a comparative analysis. Upon emergence of the reddish primary leaf on day 4 after sowing, growth slowed down by 70% and the sensitivity of the coleoptile to auxin (Indole-3-acetic acid) was lost, but turgor pressure was maintained. A quantitative comparison of the proteome (microsomal- and cytoplasmic protein fractions, respectively), using the two-dimensional difference gel electrophoresis (2-D DIGE)-technique, revealed that at least 28 proteins (spots) were differentially up- or down-regulated more than 1.5-fold. Eight of these proteins were identified by reverse-phase liquid chromatography-electrospray tandem mass spectrometry. Cessation of coleoptile growth was associated with the down-regulation (- 81 %) of subunit E of the vacuolar H(+)-ATPase (V-ATPase) and the up-regulation of enzymes involved in lignification (phenylalanine ammonia lyase) and wounding responses (xylanase inhibitor; two lipoxygenases). We conclude that the degradation of the V-ATPases, electrogenic proton pumps on the tonoplast and the membranes of the Golgi- dependent secretory pathway, may be the cause for the cessation of growth in turgid coleoptiles and the associated loss of auxin sensitivity. However, the intracellular signals that cause these proteomic changes have not yet been identified.

Identification of a novel HLA-Cw*15 variant allele, Cw*1526

A novel human leukocyte antigen (HLA)-Cw*15 variant allele was identified in a Chinese Han individual. It differs from the closest allele Cw*150201 by single nucleotide change at genomic nt 755 C>G (CDS nt 379 C>G, codon 103 CTG>GTG) in exon 3, which results in an amino acid change Leu103Val.

Genomic full length sequence of HLA-Cw*030301, identified by cloning and sequencing

Genomic full length sequence of human leukocyte antigen (HLA)-Cw*030301 that differs from Cw*030401 by two-nucleotide exchange at nt 473 (G>A) in exon 2 and nt 3033 (G>C) in 3'UTR, was identified by cloning and sequencing from a male Chinese donor.

A novel HLA-Cw*04 allele, Cw*04010103, identified by genomic full length cloning and sequencing

A novel human leukocyte antigen-Cw*04 allele, Cw*04010103, was identified by genomic full length cloning and sequencing from a male Chinese donor. It differs from the closest related allele Cw*04010101 by one nucleotide exchange at nt 1111 (G>A) in intron 3.

Yin Yang 1 regulates the transcriptional activity of androgen receptor

The multifunctional protein Yin Yang 1 (YY1) plays an important role in epigenetic regulation of gene expression. YY1 is highly expressed in various types of cancers, including prostate cancer. Currently, the mechanism underlying the functional role of YY1 in prostate tumorigenesis remains unclear. In this report, we investigated the functional interplay between YY1 and androgen receptor (AR), and the effect of YY1 on AR-mediated transcription. We found that YY1 physically interacts with AR both in a cell-free system and in cultured cells. YY1 is required for the optimal transcriptional activity of AR in promoting the transcription of the prostate specific antigen (PSA) promoter. However, ectopic YY1 expression in LNCaP cells did not further enhance the reporter driven by the PSA promoter, suggesting an optimal level of YY1 is already established in prostate tumor cells. Consistently, YY1 depletion in LNCaP cells reduced endogenous PSA levels, but overexpressed YY1 did not significantly increase PSA expression. We also observed that YY1-AR interaction is essential to YY1-mediated transcription activity of AR and YY1 is a necessary component in the complex binding to the androgen response element (ARE). Thus, our study demonstrates that YY1 interacts with AR and regulates its transcriptional activity.

Isolation and characterization of actinomycetes from healthy goat faeces

AIMS

To isolate and characterize actinomycetes with probiotic activities from healthy goat faeces.

METHODS AND RESULTS

Faecal actinomycetes were isolated by dilution methods and identified by 16S rRNA gene sequence analysis. The hydrolytic enzyme activities were analysed by clear zone formation. The antimicrobial activities and resistance to heavy metals were tested by growth inhibition methods. The isolates belong to a small group of actinobacterial genera, including Streptomyces, Nocardiopsis and Oerskovia. The Oerskovia was the most widely distributed genus among the cultures. The proportion of streptomycete-like strains producing amylase or protease is significantly higher than those of other actinomycetes (P < 0.05). Compared with streptomycete-like strains, a higher proportion of (alpha- or beta-) galactase-producing other actinomycetes was found in goat faeces. More than 50% of streptomycete-like strains showed activities against test fungi. Streptomycetes could tolerate 0.25 mmol l(-1) Cr(2)O(7)(2-), 2 mmol l(-1) Ni(2+); however, other actinomycetes are liable to 40 mmol l(-1) Fe(3+) and 0.25 mmol l(-1) Cr(2)O(7)(2-) and resistant to 5 mmol l(-1) Ni(2+) and 2 mmol l(-1) Cu(2+).

CONCLUSIONS

The different physiological characteristics of the actinomycetes suggested that the cooperation in the actinomycetes might be involved in their association with goat.

SIGNIFICANCE AND IMPACT OF THE STUDY

Probiotic mixtures based on faecal actinomycetes showed potentials in animal production.

High-resolution three-dimensional imaging of the rich membrane structures of bone marrow-derived mast cells

Atomic force microscopy (AFM) enables high-resolution three-dimensional (3D) imaging of cultured bone marrow-derived mast cells. Cells were immobilized by a quick centrifugation and fixation to preserve their transient cellular morphologies followed by AFM characterization in buffer. This "fix-and-look" approach preserves the structural integrity of individual cells. Well-known membrane morphologies, such as ridges and microvilli, are visualized, consistent with prior electron microscopy observations. Additional information including the 3D measurements of these characteristic features are attained from AFM topographs. Filopodia and lamellopodia, associated with cell spreading, were captured and visualized in three dimensions. New morphologies are also revealed, such as high-density ridges and micro-craters. This investigation demonstrates that the "fix-and-look" approach followed by AFM imaging provides an effective means to characterize the membrane structure of hydrated cells with high resolution. The quantitative imaging and measurements pave the way for systematic correlation of membrane structural features with the biological status of individual cells.

Moment switching in nanotube magnetic force probes

Magnetic images of high density vertically recorded media using metal-coated carbon nanotube tips exhibit a doubling of the spatial frequency under some conditions (Deng et al 2004 Appl. Phys. Lett. 85 6263). Here we demonstrate that this spatial frequency doubling is due to the switching of the moment direction of the nanotube tip. This results in a signal which is proportional to the absolute value of the signal normally observed in MFM. Our modeling indicates that a significant fraction of the tip volume is involved in the observed switching, and that it should be possible to image high bit densities with nanotube magnetic force sensors.