Initial subduction-related magmatism in southern Alaska identified by geochemistry and zircon Hf-O isotopes

Abundant arc-type magmatic and metamorphic rocks exist on Earth today, which provide insights into the equilibrium state of the subduction process. However, magmatic samples generated during the initial stage of subduction is largely unknown. This hinders our understanding of the subduction initiation process and by inference, the onset of plate tectonics as well as the history of crustal formation. To address this issue, we carried out a comprehensive geochemical-geochronological study of a suite of Late Triassic to mid-Jurassic plutonic rocks from southern Alaska that potentially represent magmas from the initial to mature stages of arc formation. While all studied samples show typical arc-type geochemical signatures, i.e., enrichment of large ion lithophile elements (LILEs) and depletion of high field strength elements (HFSEs) relative to the heavy rare earth elements (HREEs), the Late Triassic trondhjemites show unique geochemical features such as strongly positive ε_Hf(t) and ε_Nd(t) coupled with lower δ¹⁸O (average 4.77‰ ± 0.09‰). These signatures, along with its higher zircon saturation temperatures compared with younger plutonic rocks, are best explained by shallow partial melting of subducting high-temperature hydrothermally altered lower oceanic crust (i.e., gabbro). If true, these surprising findings would open up new ways to study subduction initiation which would have important bearing on future research on the onset of global plate tectonics and the formation of the continental crust.

Pliocene-Quaternary crustal melting in central and northern Tibet and insights into crustal flow

There is considerable controversy over the nature of geophysically recognized low-velocity–high-conductivity zones (LV–HCZs) within the Tibetan crust, and their role in models for the development of the Tibetan Plateau. Here we report petrological and geochemical data on magmas erupted 4.7–0.3 Myr ago in central and northern Tibet, demonstrating that they were generated by partial melting of crustal rocks at temperatures of 700–1,050 °C and pressures of 0.5–1.5 GPa. Thus Pliocene-Quaternary melting of crustal rocks occurred at depths of 15–50 km in areas where the LV–HCZs have been recognized. This provides new petrological evidence that the LV–HCZs are sources of partial melt. It is inferred that crustal melting played a key role in triggering crustal weakening and outward crustal flow in the expansion of the Tibetan Plateau.

The role of the low velocity-high conductivity zones (LV–HCZs) in developing the Tibetan Plateau has remained controversial. Here, Wang et al. present new geochemical and petrological data that show the LV–HCZs are sources of partial melt thus giving insight into the development of the Tibetan Plateau.

Linking magmatism with collision in an accretionary orogen

A compilation of U-Pb age, geochemical and isotopic data for granitoid plutons in the southern Central Asian Orogenic Belt (CAOB), enables evaluation of the interaction between magmatism and orogenesis in the context of Paleo-Asian oceanic closure and continental amalgamation. These constraints, in conjunction with other geological evidence, indicate that following consumption of the ocean, collision-related calc-alkaline granitoid and mafic magmatism occurred from 255 ± 2 Ma to 251 ± 2 Ma along the Solonker-Xar Moron suture zone. The linear or belt distribution of end-Permian magmatism is interpreted to have taken place in a setting of final orogenic contraction and weak crustal thickening, probably as a result of slab break-off. Crustal anatexis slightly post-dated the early phase of collision, producing adakite-like granitoids with some S-type granites during the Early-Middle Triassic (ca. 251–245 Ma). Between 235 and 220 Ma, the local tectonic regime switched from compression to extension, most likely caused by regional lithospheric extension and orogenic collapse. Collision-related magmatism from the southern CAOB is thus a prime example of the minor, yet tell-tale linking of magmatism with orogenic contraction and collision in an archipelago-type accretionary orogen.

Magmatic record of India-Asia collision

New geochronological and geochemical data on magmatic activity from the India-Asia collision zone enables recognition of a distinct magmatic flare-up event that we ascribe to slab breakoff. This tie-point in the collisional record can be used to back-date to the time of initial impingement of the Indian continent with the Asian margin. Continental arc magmatism in southern Tibet during 80–40 Ma migrated from south to north and then back to south with significant mantle input at 70–43 Ma. A pronounced flare up in magmatic intensity (including ignimbrite and mafic rock) at ca. 52–51 Ma corresponds to a sudden decrease in the India-Asia convergence rate. Geological and geochemical data are consistent with mantle input controlled by slab rollback from ca. 70 Ma and slab breakoff at ca. 53 Ma. We propose that the slowdown of the Indian plate at ca. 51 Ma is largely the consequence of slab breakoff of the subducting Neo-Tethyan oceanic lithosphere, rather than the onset of the India-Asia collision as traditionally interpreted, implying that the initial India-Asia collision commenced earlier, likely at ca. 55 Ma.

Patient perception and knowledge on total joint replacement surgery

OBJECTIVES

To study patients' perceptions and knowledge about total joint replacement surgery. DESIGN; Cross-sectional survey. SETTING; University teaching hospital, Hong Kong.

PATIENTS

Three hundred consecutive patients with the diagnosis of osteoarthritis or inflammatory arthritis attending the out-patient clinic from June 2010 to May 2011.

MAIN OUTCOME MEASURES

Patients' knowledge and how they got the knowledge about total joint replacement surgery, and concerns about the outcome of such operations.

RESULTS

Whilst 94% of the patients knew about total joint replacement surgery, 77% obtained such knowledge from their friends and relatives. The three most common concerns related to this type of operation were whether they might: be wheelchair bound after surgery (64%), need to be taken care of by others for more than 3 months (61%), and have post-surgery complications (54%). Most of them recognised the advantages of the surgery, 82% knew about good pain relief after surgery, and 87% realised that total joint replacement surgery could improve their mobility. Patients did not have a realistic idea regarding the survival of the prosthesis; 41% thought the prosthesis might last for less than 10 years and 34% had no idea about its longevity. CONCLUSION; Patients did recognise the advantages of total joint replacement surgery in treating arthritis. However, they had many concerns about its outcome that warrant clarification. Public education on these aspects is necessary to address concerns, and may be achieved in cooperation with the media.

The amount of recycled crust in sources of mantle-derived melts

Plate tectonic processes introduce basaltic crust (as eclogite) into the peridotitic mantle. The proportions of these two sources in mantle melts are poorly understood. Silica-rich melts formed from eclogite react with peridotite, converting it to olivine-free pyroxenite. Partial melts of this hybrid pyroxenite are higher in nickel and silicon but poorer in manganese, calcium, and magnesium than melts of peridotite. Olivine phenocrysts' compositions record these differences and were used to quantify the contributions of pyroxenite-derived melts in mid-ocean ridge basalts (10 to 30%), ocean island and continental basalts (many >60%), and komatiites (20 to 30%). These results imply involvement of 2 to 20% (up to 28%) of recycled crust in mantle melting.

Evaluation of survival rate after follicular unit transplantation using the KNU implanter

BACKGROUND

Many hair transplant surgeons have advocated the use of micrograft megasessions for the purpose of a more natural looking end result, especially in the Oriental with higher skin/hair color contrast and darker, coarse, straight hairs. But it also has some fundamental limitations. Most important are a low graft yield and a low density after transplantation. There are several reports about the survival rate of micrografts in Caucasians, though the results are variable, but few reports about the survival rate and fate of micrografts in Orientals.

OBJECTIVE

To compare the survival rate of one-hair follicular units with that of two-hair follicular units using the KNU implanter, to ascertain the average survival rate of micrografts (one- and two-hair follicular units), and to evaluate the fate of grafted hair according to time.

METHODS

Two templates of 1.5 cm2 were made by tattooing on both sides of the frontoparietal recess areas in 11 patients with male pattern baldness (beyond Norwood type IIIa). The authors planted one-hair unit micrografts in the left template and two-hair unit micrografts in the right template, which were prepared by the concept of follicular unit, and counted the surviving number of follicular units at 1 and 3 months and total hairs at 6 and 12 months after transplantation.

RESULTS

The mean survival rate by the number of follicular units was 47.3 and 57.4% at 1 and 3 months after transplantation, respectively. The mean survival rate by the total number of hairs was 92.0 and 90.4% at 6 and 12 months after transplantation, respectively.

CONCLUSION

About 50% of the transplanted hairs fell out in 1 month, but at 6 months the survival rate of follicular unit transplantation using the KNU implanter showed a good result (92%), and there were no significant differences in the mean survival rate of follicular unit and total hairs between one-hair and two-hair units at 1, 3, 6, and 12 months after transplantation.

A case of Dowling-Degos disease suggesting an evolutional sequence

We report a 47-year-old woman who presented with asymptomatic reticulate hyperpigmentations on the neck, lateral face, axillae, trunk, inguinal areas, and dorsa of both hands and feet. We thought it was an unusual case in the spectrum between the pole of Dowling-Degos disease (DDD) and that of reticulate acropigmentation of Kitamura (RAK). Another interesting point was that the biopsied specimens from the abdomen, neck, and axillary lesions showed somewhat different histopathologic features from typical DDD, suggesting an evolutional sequence. From these findings we suggest that a lichenoid inflammation may be responsible for the typical maculo-papular lesions of DDD.

Fatal hemoptysis in dissecting aortic aneurysm and salmonellosis: a case report

Hemoptysis is a rare manifestation of dissecting aortic aneurysm and aortobronchial fistula may occur when an aortic aneurysm is mycotic, atherosclerotic, traumatic or postoperative. Aortobronchial fistulas are generally fatal if not treated surgically. An aggressive diagnostic approach to patients with hemoptysis and prompt surgical intervention in those suspected of aortobronchial fistulas should result in additional survivors. Imaging studies, including chest radiography, chest computerized tomography, arteriography and bronchoscopy provide useful diagnostic information. However, challenges remain when we encounter this condition. Sometimes, the final exsanguinating hemorrhage is preceded by a distinct prodromal period of intermittent hemoptysis. This allows clinicians time to recognize such fistulas and perform emergency surgery. We present a patient with this condition to alert clinicians to this potentially deadly cause of hemoptysis.

Female bladder neck changes with position

Location of the bladder neck and its dynamic motion are believed to be influenced by body position. This study was designed to evaluate factors affecting bladder neck mobility in both supine and standing positions. The parameters of 75 GSI patients and 49 controls were compared by Student's t-test. Receiver operating characteristic curves and multiple logistic regression analysis were used to analyze the effects of potential contributing factors on bladder neck mobility. We were unable to find any significant correlation between bladder neck hypermobility and GSI. We also failed to demonstrate that bladder neck hypermobility in the supine or standing position relative to previous believed risk factors, including parity, vaginal delivery, menopause, cystocele, rectocele, uterine prolapse or body mass index. In order to elucidate the pathophysiology of bladder neck mobility clearly, changes in intraabdominal pressure and gravitational direction in different positions should be evaluated carefully and scientifically in further studies.

Outbreak of rat mite dermatitis in medical students

BACKGROUND

The tropical rat mite, Ornithonyssus bacoti (0. bacoti), is an ectoparasite on many rodents, but when the rodent is not available, humans may become the victim of the mite's bite. The bite induces a nonspecific dermatitis; therefore, it is not easy to diagnose rat mite dermatitis unless the parasites are found.

MATERIALS AND METHODS

Ten cases of rat mite dermatitis were found in medical students who had studied in the same room of the library. Their nonspecific dermatitis consisted of small papules, and parasites were found in the skin or in the environment. The mites were collected and identified as O. bacoti, female. Histopathologic studies showed moderate perivascular lymphohistiocytic infiltrations intermingled with some eosinophils. The presence of rodents in or around the room was confirmed by the students, but there had been no preceding rodent eradication. Although the rats were not captured in the library, insecticides were sprayed, and no further problem with either mites or dermatitis developed during the follow-up period.

CONCLUSIONS

Rat mite dermatitis can occur in clusters that involve a common source of exposure to the rat mite epidemiologically. Prompt identification of rat mites and the eradication of mites and rodents from the environment can prevent further spreading of the disease.

Lipid composition of the stratum corneum of the sole in patients with leprosy

Several reports support the view that changes of composition of the stratum corneum (SC) lipids may be the cause of impaired barrier function which, in turn, gives rise to xerosis and ichthyotic skin in leprosy. Many reports about abnormalities of serum lipids and cutaneous manifestations, such as xerosis and ichthyotic changes in leprosy, led us to the idea that the composition of SC lipids in patients with leprosy may be different from that in normal subjects. However, the many studies done in the past do not sufficiently account for this. To investigate the composition of SC lipids in patients with leprosy, thin-layer chromatography (TLC) was undertaken. Extraction of the SC lipids with a methanolchloroform-H2O mixture (4:2:1.6, v/v/v, Bligh-Dyer solvent) was carried out after shaving of the SC from the sole. TLC was performed and the composition of lipids was quantitated by photodensitometry. Our study revealed that the composition of SC lipids in the anesthetic lesions of leprosy patients was higher in cholesterol sulfate and triglycerides and lower in sphingolipids and cholesterol esters than that of normal subjects.

Acetylcholine potentiation of field stimulated rat vas deferens: a pre-synaptic muscarinic mechanism?

Acetylcholine (ACh) was found to markedly enhance the nerve stimulation induced twitch response of isolated, field-stimulated rat vas deferens (RVD). The ED200 (concentration which enhances the twitch response to 200% of control) for this potentiation was 6 X 10(-6)M with the maximum twitch response being increased by more than 3 fold (325 +/- 30%). Carbachol (ED200 = 8.5 X 10(-7)M) showed identical results. With each drug the potentiation was competitively antagonized by atropine (10(-7) - 10(-5)M). Physostigmine 10(-8) - 10(-6)M) both enhanced the basal twitch response (215 +/- 8% of control at 10(-5)M) and the sensitivity of the RVD to ACh (ED200 = 3.3 X 10(-7)M) but not to carbachol. Atropine, on the other hand reduced the basal twitch response by 18 +/- 3% at 10(-5)M. Hemicholinium (10(-4)M) also reduced the basal twitch responses by 23 +/- 5%. ACh (10(-7)M - 10(-5)M) did not modify the responses of unstimulated RVD to norepinephrine or KCl suggesting a pre-synaptic site of action. Taken together these results are compatible with the presence of a pre-junctional, excitatory muscarinic mechanism in the field stimulated RVD. That this cholinergic system may be of physiological significance is supported by the observations that atropine and hemicholinium depress while physostigmine enhances the twitch response in the absence of exogenous ACh.